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EARTH 

SCIENCES 
LIBIARY 


GIFT   OF 
Miss  Frances  M.  Molera 


I 


INTERNATIONA!  SCIENTIFIC  SERIES. 


NO.  n. 


THE  second  volume  of  this  scries  is  an  original  and  suggestive  work, 
entitled 


PHYSICS  AND  POLITICS; 

OR, 

glitg  oq  tl\e  Sppli(Tatior\  of  tl^e  Pfiqdiple  of 
"  JNfatitfal  $eledtion  "  ai)d  "  I^efitki^de  " 
to  Political  ^odiety. 

By  WALTER  BAGEHOT,  Esq., 

A.ntlior  of  "The  Englisli  Constitxitioix." 


It  is  now  ready,  and  will  be  published  in  Xovember. 

D.   APPLETON    &   CO. 


THE 


INTERNATIONAL    SCIENTIFIC    SERIES 

VOL.    I. 


THE  FORMS  OF  WATER 


CLOUDS   Sf   RIVERS,    ICE    $    GLACIERS 


BY 


JOHN   TYNDALL,  LL.D.  F.E.S. 


PROFKSSOR    OF     NATURAL    PHILOSOPHY     IN     THE     ROYAL    INSTITUTION 


WITH     THIRTY- FIVE     ILLUSTRATIONS    DRAWN     AND     ENGRAVED 
UNDER    THE    DIRECTION    OF    THE    AUTHOR 


NEW  YOEK: 
D.    APPLETON    AND    COMPANY, 

649    &    551    BROADWAY. 
1872. 


ENTERED,  according  to  Act  of  Congress,  in  the  year  1872, 

BY  D.  APPLETON  &  CO., 
In  the  Office  of  the  Librarian  of  Congress,  at  Washington. 


EARTH 

SCIENCES 

LIBRARY 


AMERICAN  PREFACE 


TO   THE 


INTERNATIONAL  SCIENTIFIC  SERIES. 


THE  rapid  development  of  science  in  the  present  age, 
and  the  increasing  public  interest  in  its  results,  make  it 
desirable  that  the  most  efficient  measures  should  be  adopted 
to  elevate  the  character  of  its  popular  literature.  The  ten- 
dency of  careless  and  unscrupulous  book-makers  to  cater  to 
public  ignorance  and  love  of  the  marvellous,  and  to  foist  their 
crude  productions  upon  those  who  are  too  little  instructed  to 
judge  of  their  real  quality,  has  hitherto  been  so  strong  as  to 
cast  discredit  upon  the  idea  of  "  popular  science."  It  is 
highly  important  to  counteract  this  evil  tendency  by  fur- 
nishing the  public  with  popular  scientific  books  of  a  superior 
character.  The  publication  of  the  present  volume  is  the  first 
step  in  carrying  out  a  systematic  enterprise  of  this  kind.  It 
initiates  a  series  of  such  works  on  a  wide  range  of  scientific 
subjects,  to  be  prepared  by  the  leading  thinkers  of  different 
countries,  and  known  as  the  "  INTERNATIONAL  SCIENTIFIC 
SERIES." 


vi  AMERICAN  PREFACE. 

It  is  designed  to  consist  of  compendious  scientific  trea- 
tises, representing  the  latest  advances  of  thought  upon  sub- 
jects of  general  interest,  theoretical  and  practical,  to  all 
classes  of  readers.  The  familiar  phenomena  of  surrounding 
Nature,  in  their  physical  and  chemical  aspects,  the  knowledge 
of  which 'has  recently  undergone  marked  extension  or  revision, 
will  be  considered  in  their  latest  interpretations.  Biology,  or 
the  general  science  of  life,  which  has  lately  come  into  promi- 
nence, will  be  explained  in  its  leading  and  most  important 
principles.  The  subject  of  mind,  which,  under  the  inductive 
method  and  on  the  basis  of  its  physical  accompaniments  and 
conditions,  is  giving  rise  to  a  new  psychology,  will  be  treated 
with  the  fulness  to  which  it  is  entitled.  The  laws  of  man's 
social  development,  or  the  natural  history  of  society,  which 
are  now  being  studied  by  the  scientific  method,  will  also  re- 
ceive a  due  share  of  attention.  While  the  books  of  this 
series  are  to  deal  with  a  wide  diversity  of  topics,  it  will  be  a 
leading  object  of  the  enterprise  to  present  the  bearings  of 
inquiry  upon  the  higher  questions  of  the  time,  and  to  throw 
the  latest  light  of  science  upon  the  phenomena  of  human 
nature  and  the  economy  of  human  life. 

As  the  first  requisite  of  such  a  series  of  works  is  trust- 
worthiness, their  preparation  has  been  confided  only  to  men 
of  eminent  ability,  and  who  are  recognized  authorities  in 
their  several  departments.  As  they  are  to  address  the  non- 
scientific  public,  it  is  a  further  requisite  that  they  should  be 
written  in  familiar  and  intelligible  language.  It  is  not  to  be 
expected  that  the  authors  will  all  attain  to  the  same  stand- 
ard in  this  respect,  but  they  are  pledged  to  the  utmost  sim- 


AMERICAN  PREFACE.  yii 

plicity  of  exposition  that  is  possible  consistently  with  clear 
and  accurate  representation. 

As  science  is  now  the  supreme  interest  of  civilization,  and 
concerns  alike  the  people  of  every  country,  and  as,  moreover, 
it  affords  a  common  ground  upon  which  men  of  all  races, 
tongues,  faiths,  and  nationalities,  may  work  together  in  har- 
mony, it  seemed  fitting  that  an  undertaking  of  this  kind 
should  be  of  comprehensive  scope  and  stand  upon  an  inter- 
national basis.  With  the  growing  sentiment  of  sympathy 
and  brotherhood  amor-g  the  most  widely-separated  students 
of  Nature,  and  the  extensive  facilities  of  business  intercourse 
that  now  exist,  there  appeared  no  reason  why  an  interna- 
tional combination  of  authors  and  publishers  should  not  be 
effected  that  would  be  equally  favorable  to  their  own  private 
interests  and  advantageous  to  the  public.  To  gain  this  end 
and  guarantee  to  authors  better  remuneration  for  their  work, 
is  a  distinctive  purpose  of  the  present  enterprise.  But  there 
was  this  difficulty  in  the  way  of  any  such  arrangement,  that, 
while  the  rights  of  foreign  authors  are  guarded  by  all  other 
civilized  governments,  they  are  not  protected  by  the  gov- 
ernment of  the  United  States.  To  escape  this  difficulty,  and 
secure  American  cooperation,  the  first  thing  needed  was  to 
obtain  the  consent  of  an  American  publishing-house  to 
grant  voluntarily  to  foreign  authors  the  justice  which  our 
government  denies  them.  It  was  agreed  by  Messrs.  Apple- 
ton  that  they  would  pay  the  foreign  contributors  to  this 
series  the  full  rates  of  copyright  that  are  usually  allowed  to 
American  authors.  When  this  was  done,  engagements 
were  made  with  distinguished  scientists  of  England,  France, 


viii  AMERICAN  PREFACE. 

Germany,  and  the  United  States,  to  prepare  works  for  the 
series,  and  with  Henry  S.  King  &  Co.,  of  London,  Germer 
Bailliere,  of  Paris,  and  Messieurs  Brockhaus,  of  Leipsic,  to 
publish  them.  Negotiations  are  pending  for  the  reproduc- 
tion of  the  series  in  other  countries,  but  the  present  arrange- 
ments secure  to  the  authors  the  benefits  of  the  four  leading 
markets  of  the  world. 

It  is  a  fact  not  without  significance,  that  the  proposal  of 
this  enterprise  was  received  with  the  most  cordial  favor  by 
the  eminent  scientific  men  who  were  solicited  to  aid  in  carry- 
ing it  forward.  Most  of  them  consented  at  once ;  but,  while 
some  were  so  heavily  burdened  with  work  that  they  could 
enter  into  no  immediate  engagements,  not  one  of  them  de- 
clined to  cooperate,  and  all  promised  to  do  so  at  the  earliest 
practicable  opportunity.  The  feeling  of  the  desirableness 
of  such  an  undertaking  was  strong  and  unanimous.  The  old 
dislike  of  the  cultivators  of  science  to  participate  in  the  work 
of  popular  teaching,  seems  very  much  to  have  passed  away ; 
and  in  England,  France,  and  Germany,  alike  it  was  freely  ac- 
knowledged that  savants  have  an  imperative  duty  to  dis- 
charge in  relation  to  the  work  of  general  scientific  educa- 
tion. As  remarked  by  Prof.  Virchow,  of  Berlin,  "  the  des- 
tiny of  science  is  the  service  of  humanity." 

It  was  stipulated  by  the  authors  that  they  should  have 
ample  time  for  the  preparation  of  their  books,  and,  as  the 
arrangements  were  recently  made,  only  a  few  of  the  works 
are  yet  ready.  Several,  however,  arc  now  in  press,  and  will 
shortly  appear. 

Those  interested  in  the  series  are  under  many  obligations 


AMERICAN  PREFACE.  jx 

to  Prof.  Tyndall  for  his  kindness  in  consenting  to  furnish 
its  commencing  volume.  Being  prepared  in  a  short  time, 
amid  great  pressure  both  of  laboratory  and  literary  work,  it 
contains  somewhat  less  matter  than  may  be  expected  in  the 
ensuing  volumes.  It  treats  of  subjects  upon  which  he  is  per- 
haps the  highest  living  authority ;  and  is  an  admirable  ex- 
ample of  that  vivid,  stirring,  impressive  style  for  which  its 
author  is  so  distinguished.  Prof.  Tyndall  is  not  only  a  mas- 
ter in  the  "  scientific  use  of  the  imagination,"  but  in  kindling 
the  action  of  that  faculty  in  his  readers.  He  writes  in  pict- 
ures, so  as  to  make  them  see  what  he  sees.  In  this  volume 
he  addresses  himself  directly  to  his  juvenile  friends,  groups 
them  around  him,  takes  them  with  him  to  his  favorite  moun- 
tains, and  thus  adds  a  dramatic  element  and  the  effect  of 
personal  sympathy  to  familiar  colloquial  exposition. 

The  "  INTERNATIONAL  SCIENTIFIC  SEKIES  "  will  form  an 
elegant  and  valuable  library  of  popular  science,  fresh  in  treat- 
ment, attractive  in  form,  strong  in  character,  moderate  in 
price,  and  indispensable  to  all  who  care  for  the  acquisition 
of  solid  and  serviceable  knowledge ;  and  it  is  commended  to 
American  readers  as  a  help  in  the  important  work  of  sound 
public  education. 

E.  L.  T. 

NEW  YORK,  September,  1872. 


AUTHOR'S  PREFACE. 


AFTER  an  absence  of  twelve  years,  I  visited  the  Mer 
de  Glace  last  June.  It  exhibited  in  a  striking  degree 
that  excess  of  consumption  over  supply,  which,  if  contin- 
ued, will  eventually  reduce  the  Swiss  glaciers  to  the  mere 
spectres  of  their  former  selves.  When  I  first  saw  the 
Mer  de  Glace  its  ice-cliffs  towered  over  Les  Mottets,  and 
an  arm  of  the  Arveiron,  issuing  from  the  cliffs,  plunged 
as  a  powerful  cascade  down  the  rocks.  The  ice  has  now 
shrunk  far  behind  them.  A  huge  moraine,  left  behind 
by  the  retreating  glacier,  will  mark,  for  some  time  to 
come,  its  recent  magnitude.  The  vault  of  the  Arveiron 
has  dwindled  considerably.  The  way  up  to  the  Chapeau 
lies  on  the  top  of  a  lateral  moraine,  reached  a  few  years  ago 
by  the  surface  of  the  glacier,  the  present  surface  lying  far 
below.  The  visible  and  continual  breaking  away  of  the 
moraines,  left  thus  stranded  on  the  mountain-flank,  ex- 
plains the  absence  of  ancient  ridges  on  the  mountains 


xii  PREFACE. 

where  the  slopes  are  steep.  The  ice-cascade  of  the  Geant 
has  suffered  much  from  the  general  waste.  Its  crevasses 
are  still  wild,  but  the  ice- cliffs  and  seracs  of  former  days 
are  but  poorly  represented  to-day. 

The  great  Aletsch  and  its  neighbors  exhibit  similar 
evidences  of  diminution.  I  found,  moreover,  this  year, 
that  the  two  ancient  moraines  mentioned  in  paragraph 
364  are  parts  of  the  same  great  lateral  moraine  which 
flanked  the  glacier  for  a  long  period,  during  which  its 
magnitude  must  have  remained  practically  constant.  The 
place  occupied  by  the  ancient  ice-river  is  rendered  strik- 
ingly conspicuous  by  this  well-preserved  boundary. 

During  my  residence  at  the  Bel  Alp  this  year,  a 
catastrophe  occurred  which  renders,  for  the  time  being, 
the  description  of  the  Margelin  See  given  in  §  50  inap- 
propriate. In  company  with  two  young  friends  I  had 
descended  the  glacier  and  passed  through  the  gorge  of 
the  Massa.  On  our  return  to  the  Bel  Alp  we  found  the 
domestics  of  the  hotel  leaning  out  of  the  windows  and 
looking  excitedly  towards  the  glacier.  From  it  pro- 
ceeded a  sound  which  resembled  the  roar  of  a  cataract. 
The  servants  remarked  that  the  Margelin  See  must  have 
broken  loose.  This  was  the  case.  For  a  time,  however, 
the  water  flowed  beneath  the  glacier;  but  at  a  point 
about  midway  between  the  Bel  Alp  and  the  ^Eggisch- 
horn,  it  broke  forth  on  the  -^Eggischhorn  side,  and  formed 


PKEFACE.  xiii 

a  torrent  between  the  glacier  and  the  slope*  of  the  moun- 
tain. In  some  places  this  river  was  more  than  sixty 
yards  wide,  at  others  it  was  contracted  to  less  than  one- 
fifth  of  this  width.  Broken  cascades  of  great  height  were 
formed  here  and  there  by  successive  ledges  of  ice,  the 
torrent  leaping  with  indescribable  fury  from  ledge  to 
ledge,  and  sending  a  smoke  of  spray  into  the  air.  At  one 
place  the  bottom  of  the  torrent  was  deep  soft  sand,  which, 
after  the  water  had  passed,  could  be  seen  to  have  been 
tortured  into  huge  funnels  by  the  whirling  eddies  over- 
head. 

Soon  after  we  reached  the  Bel  Alp,  on  the  occasion 
just  referred  to,  the  front  of  the  torrent  appeared  at  the 
opposite  side  of  the  valley  carrying  everything  movable 
before  it,  and  immediately  afterwards  swept  through  the 
hollow  that  we  had  traversed  a  little  earlier  in  the 
day.  When  at  the  end  of  the  glacier  I  was  struck  by 
the  force  and  volume  of  the  Massa,  and  the  grandeur 
of  its  vault,  but  I  could  not  then  account  for  the  huge 
blocks  of  ice  which  it  incessantly  carried  down.  Doubt- 
less the  eruption  above  had  been  partial  before  the  grand 
rush  set  in.  The  Rhone  was  considerably  swollen,  crops 
were  damaged  or  ruined,  and  the  driver  of  the  diligence 
was  sorely  perplexed  to  find  himself  in  three  feet  of 
water,  without  any  apparent  reason,  on  the  public  high- 
way. Two  or  three  days  subsequently  I  learned  at  the 


Xiv  PREFACE. 

^Eggischhorn  that  an  engineer  had  been  sent  up  to  re- 
port on  the  possibility  of  opening  a  channel,  so  as  to  pre- 
vent any  future  accumulation  of  water  in  the  Margelin 
See.  If  this  be  done,  a  useful  end  will  be  gained,  by  the 
abolition,  however,  of  one  of  the  most  beautiful  objects  in 
Switzerland. 

J.  TYNDALL. 

September,  1872. 


CONTENTS. 


PAOB 

}  1,  2.  Clouds,  Rains,  and  Rivers         .  .  .  .  .1,6 

3.  The  Waves  of  Light          .  .  .  .  .  .8 

4.  The  Waves  of  Heat  which  produce  the  Vapour  of  our  Atmosphere 

and  melt  our  Glaciers  .  .  .  .  .  .11 

5.  Experiments  to  prove  the  foregoing  statements  .  .  .14 

6.  Oceanic  Distillation  .  .  .  .  .  .19 

7.  Tropical  Rains       .  .  .  .  .  .  .23 

8.  Mountain  Condensers        .  .  .  ,  .  .27 

9.  Architecture  of  Snow         .  .  .  .  .  .29 

10.  Atomic  Poles          .  .  .  .  .  .  .32 

11.  Architecture  of  Lake  Ice    .  .  .  .  .  .35 

12.  The  Source  of  the  Arveiron.    Ice  Pinnacles,  Towers,  and  Chasms 

of  the  Glacier  des  Bois.    Passage  to  the  Montanvert   .  .38 

13.  The  Mer  de  Glace  and  its  Sources.    Our  First  Climb  to  the  Cleft 

Station  ........     43 

14.  Ice-cascade  and  Snows  of  the  Col  du  G6ant  .  .  .46 

1 5.  Questioning  the  Glaciers   .  ,  .  .  .  .48 
10.  Branches  and  Medial  Moraines  of  the  Mer  de  Glace  from  the 

Cleft  Station     .  .  .  .  .  .  .51 

17.  The  Talefre  and  the  Jardin.    Work  among  the  Crevasses  .    52 

18.  First  Questions  regarding  Glacier  Motion.    Drifting  of  Bodies 

buried  in  a  Crevasse  .    64 


XVI  CONTENTS. 

PAGH 

§  19.  The  Motion  of  Glaciers.    Measurements  by  Hugi  and  Agassiz. 

Drifting  of  Huts  on  the  Ice            .            .            .  .59 

20.  Precise  Measurements  of  Agassiz  and  Forbes.  Motion  of  a  Glacier 

proved  to  resemble  the  Motion  of  a  Biver     .            .  .60 

21.  The  Theodolite  and  its  Use.     Our  own  Measurements  .  .       62 

22.  Motion  of  the  Mer  de  Glace      .            .            .            .  .66 

23.  Unequal  Motion  of  the  two  Sides  of  the  Mer  de  Glace  .  .       70 

24.  Suggestion  of  a  new  Likeness  of  Glacier  Motion  to  Kiver  Motion. 

Conjecture  tested       .            .            .            .            .  .72 

25.  New  Law  of  Glacier  Motion       .            .            .            .  .76 

26.  Motion  of  Axis  of  Mer  de  Glace            .            .            .  .78 

27.  Motion  of  Tributary  Glaciers     .            .            .            .  .79 

28.  Motion  of  Top  and  Bottom  of  Glacier   .            .            .  .80 

29.  Lateral  Compression  of  a  Glacier           .            .            .  .81 

30.  Longitudinal  Compression  of  a  Glacier  .            .            .  .84 

31.  Sliding  and  Flowing.     Hard  Ice  and  Soft  Ice    .            .  .      86 

32.  Winter  on  the  Mer  de  Glace      .            .            .            .  .88 

33.  "Winter  Motion  of  the  Mer  de  Glace       ...  93 

r 

34.  Motion  of  the  Grlndelwald  and  Aletsch  Glacier  .       93 

35.  Motion  of  Morteratsch  Glacier .            .            .            .  .95 

36.  Birth  of  a  Crevasse :  Keflections            .            .            .  .98 

37.  Icicles    .....•,.       99 

38.  The  Bergschrund           .            .            .            .            .  .102 

39.  Transverse  Crevasses     .            .            .            •            .  .103 

40.  Marginal  Crevasses        .            .            .            .            .  .105 

41.  Longitudinal  Crevasses .            .            .            .            .  .109 

42.  Crevasses  in  relation  to  Curvature  of  Glacier    .            .  .110 
^*  43.  Moraine-ridges,  Glacier  Tables,  and  Sand  Cones           .  .112 
—  44.  The  Glacier  Mills  or  Moulins    .            .            .            .  .116 

45.  The  Changes  of  Tolume  of  Water  by  Heat  and  Cold    .  .118 


CONTENTS.  xvii 

PAQB 

§  46.  Consequences  flowing  from  the  foregoing  Properties  of  Water. 

Correction  of  Errors    .             .             .             .             .  .122 

47.  The  Molecular  Mechanism  of  Water-Congelation          .  .     125 

-  48.  The  Dirt  Bands  of  the  Mer  de  Glace    .            .            .  .127 

49.  Sea-ice  and  Icebergs      .             .             .             .             .  .132 

50.  The  JEggischhorn,  the  Margelin  See  and  its  Icebergs   .  .136 

51.  The  Bel  Alp      .......     139 

52.  The  Eiffelberg  and  G-6'rner  Glacier        .            .            .  .140 
63.  Ancient  Glaciers  of  Switzerland             .             .             .  .145 

54.  Erratic  Blocks    .             .             .             .             .             .  .147 

55.  Ancient  Glaciers  of  England,  Ireland,  Scotland,  and  Wales  .     150 

56.  The  Glacier  Epoch        .            .            .            .            .  .152 

57.  Glacial  Theories             .            .            .            .            .  .155 

58.  Dilatation  and  Sliding  Theories             .            .            .  .155 

59.  Plastic  Theory  .             .             .             .                          .  .156 

60.  Viscous  Theory .             .             .             .             .             .  .161 

61.  Eegelation  Theory          .             .             .             .             .  .163 

62.  Cause  of  Regelation      .            .            .            .            .  .167 

63.  Faraday's  View  of  Regelation   .            .            .            .  .171 

64.  The  Blue  Veins  of  Glaciers        .             .             .             .  .176 

65.  Eelation  of  Structure  to  Pressure          .            .             .  .183 

66.  Slate  Cleavage  and  Glacier  Lamination            .            .  .     187 

67.  Conclusion         .  .191 


CLOUD-BANNEK  OF  THE  AIGUILLE  DU  DRTT   (par.  84  and  227.) 


THE  FOEMS  OF  WATER 

IX 

CLOUDS  AND    RIVEKS,   ICE    AND    GLACIEES. 

§  1.  Clouds,  Rains,  and  Rivers. 

1.  EVERT  occurrence  in  Nature  is  preceded  by  other 
occurrences   which   are  its   causes,  and   succeeded  by 
others  which  are  its  effects.     The  human  mind  is  not 
satisfied  with  observing  and  studying  any  natural  oc- 
currence alone,  but  takes  pleasure  in  connecting  every 
natural  fact  with  what  has  gone  before  it,  and  with 
what  is  to  come  after  it. 

2.  Thus,  when  we  enter  upon  the  study  of  rivers  and 
glaciers,   our  interest  will   be  greatly   augmented   by 
taking  into  account  not  only  their  actual  appearances, 
but  also  their  causes  and  effects. 

3.  Let   us   trace  a  river  to  its  source.     Beginning 
where  it  empties  itself  into  the  sea,  and  following  it 


2  THE  FOEMS  OF  WATEE  IN 

backwards,  we  find  it  from  time  to  time  joined  by 
tributaries  which  swell  its  waters.  The  river  of  course 
becomes  smaller  as  these  tributaries  are  passed.  It 
shrinks  first  to  a  brook,  then  to  a  stream ;  this  again 
divides  itself  into  a  number  of  smaller  streamlets, 
ending  in  mere  threads  of  water.  These  constitute 
the  source  of  the  river,  and  are  usually  found  among 
hills. 

4.  Thus  the   Severn  has   its   source   in  the  Welsh 
Mountains ;  the  Thames  in  the  Cotswold   Hills  ;   the 
Danube  in  the  hills  of  the  Black  Forest ;  the  Rhine  and 
the  Rhone  in  the  Alps ;  the  Ganges  in  the  Himalaya 
Mountains ;  the  Euphrates   near  Mount   Ararat ;    the 
Garonne  in  the  Pyrenees ;  the  Elbe  in  the  Giant  Moun- 
tains of  Bohemia ;  the  Missouri  in  the  Rocky  Mountains, 
and  the  Amazon  in  the  Andes  of  Peru. 

5.  But  it  is  quite  plain  that  we  have  not  yet  reached 
the  real  beginning    of  the  rivers.      Whence   do  the 
earliest  streams  derive  their  water  ?     A  brief  residence 
among  the  mountains  would  prove  to  you  that  they  are 
fed  by  rains.     In   dry   weather   you   would   find   the 
streams  feeble,  sometimes  indeed  quite  dried  up.     In 
wet  weather  you  would  see  them  foaming  torrents.     In 
general  these  streams  lose  themselves  as  little  threads 
of  water  upon  the  hill  sides ;  but  sometimes  you  may 
trace  a  river  to  a  definite  spring.     The  river  Albula  in 
Switzerland,  for  instance,  rushes  at  its  origin  in  con- 
siderable volume  from  a  mountain  side.     But  you  very 


CLOUDS  AND  EIVEKS,  ICE  AND  GLACIERS.  3 

soon  assure  yourself  that  such  springs  are  also  fed  by 
rain,  which  has  percolated  through  the  rocks  or  soil, 
and  which,  through  some  orifice  that  it  has  found  or 
formed,  comes  to  the  light  of  day. 

6.  But  we  cannot  end  here.     Whence  comes  the  rain 
which  forms    the   mountain    streams  ?      Observation 
enables  you  to  answer  the  question.     Eain  does  not 
come  from  a  clear  sky.     It  comes  from  clouds.     But 
what  are  clouds  ?     Is  there  nothing  you  are  acquainted 
with  which  they  resemble?    You  discover  at  once  a 
likeness  between  them  and  the  condensed  steam  of  a 
locomotive.     At  every  puff  of  the  engine  a  cloud  is  pro- 
jected into  the  air.     Watch  the  cloud   sharply :    you 
notice  that  it  first  forms  at  a  little  distance  from  the 
top  of  the  funnel.     Give  close  attention  and  you  will 
sometimes   see   a  perfectly   clear   space  between    the 
funnel  and  the  cloud.     Through  that  clear  space  the 
thing  which  makes  the  cloud  must  pass.     What,  then, 
is  this  thing  which  at  one  moment  is  transparent  and 
invisible,  and  at  the  next  moment  visible  as  a  dense 
opaque  cloud? 

7.  It  is  the  steam  or  vapour  of  water  from  the  boiler. 
Within  the  boiler  this  steam  is  transparent  and  in- 
visible;  but  to  keep  it  in  this  invisible  state  a  heat 
would  be  required  as  great  as  that  within  the  boiler. 
When  the  vapour  mingles  with  the  cold  air  above  the 
hot  funnel  it  ceases  to  be  vapour.     Every  bit  of  steam 
shrinks,  when  chilled,  to  a  much  more  minute  particle  of 


4  THE  FORMS   OF  WATER  IN 

water.  The  liquid  particles  thus  produced  form  a  kind 
of  water-dust  of  exceeding  fineness,  which  floats  in  the 
air,  and  is  called  a  cloud. 

8.  Watch  the  cloud-banner  from   the  funnel   of  a 
running  locomotive ;  you  see  it  growing  gradually  less 
dense.     It  finally  melts  away  altogether,  and  if  you 
continue  your  observations  you  will  not  fail  to  notice 
that  the  speed  of  its  disappearance  depends  upon  the 
character   of  the  day.     In  humid   weather  the   cloud 
hangs  long  and  lazily  in  the  air ;  in  dry  weather  it  is 
rapidly  licked  up.     What  has  become  of  it?     It  has 
been  reconverted  into  true  invisible  vapour. 

9.  The   drier  the  air,  and   the  hotter  the   air,   the 
greater  is  the  amount  of  cloud  which  can  be  thus  dis- 
solved in  it.     When  the  cloud  first  forms,  its  quantity 
is  far  greater  than  the  air  is  able  to  maintain  in  an  in- 
visible state.     But  as  the  cloud  mixes  gradually  with  a 
larger  mass  of  air  it  is  more  and  more  dissolved,  and 
finally  passes  altogether  from  the  condition  of  a  finely- 
divided  liquid  into  that  of  transparent  vapour  or  gas. 

10.  Make  the  lid  of  a  kettle  air-tight,  and  permit 
the  steam  to  issue  from  the  pipe ;  a  cloud  is  precipitated 
in  all  respects  similar  to  that  issuing  from  the  funnel  of 
the  locomotive. 

11.  Permit  the  steam  as  it  issues  from  the  pipe  to 
pass  through  the  flame  of  a  spirit-lamp,  the  cloud  is  in- 
stantly dissolved  by  the  heat,  and  is  not  again  precipi- 
tated.    With  a  special  boiler  and  a  special  nozzle  the 


CLOUDS  AND  EIVERS,  ICE  AND  GLACIEES.  5 

experiment  may  be  made  more  striking,  but  not  more 
instructive,  than  with  the  kettle. 

12.  Look  to  your  bedroom  windows  when  the  weather 
is  very  cold  outside ;  they  sometimes  stream  with  water 
derived  from  the  condensation  of  the  aqueous  vapour 
from  your  own  lungs.   The  windows  of  railway  carriages 
in  winter  show  this  condensation  in  a  striking  manner. 
Pour  cold  water  into  a  dry  drinking-glass  on  a  summer's 
day :  the  outside  surface  of  the  glass  becomes  instantly 
dimmed  by  the  precipitation  of  moisture.     On  a  warm 
day  you  notice  no  vapour  in  front  of  your  mouth,  but 
on  a  cold  day  you  form  there  a  little  cloud  derived 
from  the  condensation  of  the  aqueous  vapour  from  the 
lungs. 

13.  You  may  notice  in  a  ball-room  that  as  long  as  the 
door  and  windows  are  kept  closed,  and  the  room  remains 
hot,  the  air  remains  clear;  but  when  the  doors  or  windows 
are  opened  a  dimness  is  visible,  caused  by  the  precipi- 
tation to  fog  of  the  aqueous  vapour  of  the  ball-room. 
If  the  weather  be  intensely  cold  the  entrance  of  fresh 
air  may  even  cause  snow  to  fall.     This  has  been  ob- 
served in  Russian  ball-rooms ;  and  also  in  the  subterra- 
nean stables  at  Erzeroom,  when  the  doors  are  opened 
and  the  cold  morning  air  is  permitted  to  enter. 

14.  Even   on  the  driest   day  this   vapour  is   never 
absent   from    our   atmosphere.       The  vapour    diffused 
through  the  air  of  this  room  may  be  congealed  to  hoar 
frost  in    your  presence.        This  is   done   by   filling   a 


6  THE  FORMS  OF  WATER  IN 

vessel  with  a  mixture  of  pounded  ice  and  salt,  which 
is  colder  than  the  ice  itself,  and  which,  therefore,  con- 
denses and  freezes  the  aqueous  vapour.  The  surface 
of  the  vessel  is  finally  coated  with  a  frozen  fur,  so 
thick  that  it  may  be  scraped  away  and  formed  into  a 
snow-ball. 

15.  To  produce  the  cloud,  in  the  case  of  the  loco- 
motive and  the  kettle,  heat  is  necessary.     By  heating 
the  water  we  first  convert  it  into  steam,  and  then  by 
chilling  the  steam  we  convert  it  into  cloud.     Is  there 
any  fire  in  nature   which  produces  the  clouds  of  our 
atmosphere  ?     There  is :  the  fire  of  the  sun. 

16.  Thus,  by  tracing  backward,  without  any  break  in 
the  chain  of  occurrences,  our  river  from  its  end  to  its 
real  beginnings,  we  come  at  length  to  the  sun. 

§2. 

17.  There  are,  however,  rivers  which  have  sources 
somewhat  different  from  those  just  mentioned.     They 
do  not  begin  by  driblets  on  a  hill  side,  nor  can  they  be 
traced  to  a  spring.     Go,  for  example,  to  the  mouth  of 
the  river  Rhone,  and  trace  it  backwards  to  Lyons,  where 
it  turns  to  the  east.     Bending  round  by  Chambery,  you 
come  at  length  to  the  Lake  of  Geneva,  from  which  the 
river  rushes,  and  which  you  might  be  disposed  to  regard 
as  the  source  of  the  Rhone.     But  go  to  the  head  of  the 
lake,  and  you  find  that  the  Ehone  there  enters  it,  that 
the  lake  is  in  fact  a  kind  of  expansion  of  the  river. 


CLOUDS  AND  EIVEES,  ICE  AND   aLACIEKS.  7 

Follow  this  upwards ;  you  find  it  joined  by  smaller 
rivers  from  the  mountains  right  and  left.  Pass  these, 
and  push  your  journey  higher  still.  You  come  at  length 
to  a  huge  mass  of  ice — the  end  of  a  glacier — which  fills 
the  Rhone  valley,  and  from  the  bottom  of  the  glacier 
the  river  rushes.  In  the  glacier  of  the  Ehone  you  thus 
find  the  source  of  the  river  Rhone. 

18.  But  again  we  have  not  reached  the  real  begin- 
ning of  the  river.     You  soon  convince  yourself  that  this 
earliest  water  of  the  Rhone  is  produced  by  the  melting 
of  the  ice.     You  get  upon  the  glacier  and  walk  upwards 
along  it.     After  a  time  the  ice  disappears  and  you  come 
upon  snow.     If  you  are  a  competent  mountaineer  you 
may  go  to  the  very  top  of  this  great  snow-field,  and  if 
you  cross  the  top  and  descend  at  the  other  side  you 
finally  quit  the   snow,  and  get   upon  another   glacier 
called  the  Trift,  from  the  end  of  which  rushes  a  river 
smaller  than  the  Rhone. 

19.  You    soon  learn  that  the  mountain   snow  feeds 
the  glacier.     By  some  means  or  other  the  snow  is  con- 
verted into  ice.     But  whence  comes  the  snow  P     Like 
the  rain,  it  comes  from  the  clouds,  which,  as  before, 
can  be  traced  to  vapour  raised  by  the  sun.     Without 
solar  fire  we  could  have  110  atmospheric  vapour,  without 
vapour  no  clouds,  without  clouds  no  snow,  and  without 
snow  no  glaciers.     Curious  then  as  the  conclusion  may 
be,  the  cold  ice  of  the  Alps  has  its  origin  in  the  heat  of 
the  sun. 


THE  FORMS  OF  WATER  IN 


§  3.   The  Waves  of  Light. 

20.  But  what  is  the  sun  ?     We  know  its  size  and  its 
weight.     We  also  know  that  it  is  a  globe  of  fire  far 
hotter  than   any  fire  upon  earth.     But  we  now  enter 
upon  another  enquiry.     We  have   to  learn  definitely 
what  is  the  meaning  of  solar  light  and  solar  heat ;  in 
what  way  they  make  themselves  known  to  our  senses ; 
by  what  means  they  get  from  the  sun  to  the  earth,  and 
how,  when  there,  they  produce  the  clouds  of  our  atmo- 
sphere, and  thus  originate  our  rivers  and  our  glaciers. 

21.  If  in  a  dark  room  you  close  your  eyes  and  press 
the  eyelid  with  your  finger-nail,  a  circle  of  light  will  be 
seen  opposite  to  the  point  pressed,  while  a  sharp  blow 
upon  the  eye  produces  the  impression  of  a  flash  of  light. 
There  is  a  nerve  specially  devoted  to  the  purposes  of 
vision  which  comes  from  the  brain  to  the  back  of  the 
eye,  and  there  divides  into  fine  filaments,  which  are 
woven  together  to  a  kind  of  screen  called  the  retina. 
The  retina  can  be  excited  in  various  ways  so  as  to  pro- 
duce the  consciousness  of  light ;  it  may,  as  we  have 
seen,  be  excited  by  the  rude  mechanical  action  of  a  blow 
imparted  to  the  eye. 

22.  There   is   no  spontaneous  creation  of  light   by 
the  healthy  eye.     To  excite  vision  the  retina  must  be 
affected  by  something  coming  from  without.     What  is 
that   something?     In   some   way   or   other    luminous 


CLOUDS  AND  EIVEES,  ICE  AND   GLACIERS.  9 

bodies   have  the  power   of  affecting   the  retina— but 
how? 

23.  It  was   long    supposed    that  from   such   bodies 
issued,  with  inconceivable  rapidity,  an  inconceivably  fine 
matter,  which  flew  through  space,  passed  through  the 
pores  supposed  to  exist  in  the  humours  of  the  eye, 
reached  the  retina  behind,  and  by  their  shock  against 
the  retina,  aroused  the  sensation  of  light. 

24.  This  theory,  which  was  supported  by  the  greatest 
men,  among  others  by  Sir  Isaac   Newton,  was  found 
competent  to  explain  a  great  number  of  the  phenomena 
of  light,  but  it  was  not  found  competent  to  explain  all 
the  phenomena.     As  the  skill  and  knowledge  of  experi- 
menters increased,  large  classes  of  facts  were  revealed 
which  could  only  be  explained  by  assuming  that  light 
was  produced,  not  by  a  fine  matter  flying  through  space 
and  hitting  the  retina,  but  by  the  shock  of  minute  waves 
against  the  retina. 

25.  Dip  your  finger  into  a  basin  of  water,  and  cause 
it  to  quiver  rapidly  to  and  fro.     From  the  point  of  dis- 
turbance issue  small  ripples  which  are  carried  forward 
by  the  water,  and  which  finally  strike  the  basin.     Here, 
in  the  vibrating  finger,  you  have  a  source  of  agitation ; 
in  the   water  you  have   a  vehicle  through  which  the 
finger's  motion  is  transmitted,  and  you  have  finally  the 
side  of  the  basin  which  receives  the  shock  of  the  little 
waves. 

26.  In  like  manner,  according  to  the  wave  theory  of 


10  THE  FOKMS   OF  WATER  IN 

light,  you  have  a  source  of  agitation  in  the  vibrating 
atoms,  or  smallest  particles,  of  the  luminous  body ;  you 
have  a  vehicle  of  transmission  in  a  substance  which  is 
supposed  to  fill  all  space,  and  to  be  diffused  through  the 
humours  of  the  eye ;  and  finally,  you  have  the  retina, 
which  receives  the  successive  shocks  of  the  waves. 
These  shocks  are  supposed  to  produce  the  sensation  of 
light. 

27.  We  are  here  dealing,  for  the  most  part,  with 
suppositions  and  assumptions  merely.     We  have  never 
seen  the  atoms  of  a  luminous  body,  nor  their  motions, 
We  have  never  seen  the  medium  which  transmits  their 
motions,  nor  the  waves  of  that  medium.    How,  then,  do 
we  come  to  assume  their  existence  ? 

28.  Before  such  an  idea  could  have  taken  any  real 
root  in  the  human  mind,  it  must  have  been  well  disci- 
plined and  prepared  by  observations  and  calculations  of 
ordinary  wave-motion.     It  was  necessary  to  know  how 
both   water-waves   and   sound-waves   are   formed   and 
propagated.    It  was  above  all  things  necessary  to  know 
how  waves,  passing  through  the  same  medium,  act  upon 
each  other.     Thus  disciplined,  the  mind  was  prepared 
to  detect  any  resemblance  presenting  itself  between  the 
action  of  light  and  that  of  waves.     Great  classes  of 
optical  phenomena  accordingly  appeared  which  could 
be  accounted  for  in  the  most  complete  and  satisfactory 
manner  by  assuming  them  to  be  produced  by  waves,  and 
which  could   not   be   otherwise  accounted  for.     It  is 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.  11 

because  of  its  competence  to  explain  all  the  phenomena 
of  light  that  the  wave  theory  now  receives  universal 
acceptance  on  the  part  of  scientific  men. 

Let  me  use  an  illustration.  We  infer  from  the 
flint  implements  recently  found  in  such  profusion  all 
over  England  and  in  other  countries,  that  they  were 
produced  by  men,  and  also  that  the  Pyramids  of  Egypt 
were  built  by  men,  because,  as  far  as  our  experience 
goes,  nothing  but  men  could  form  such  implements  or 
build  such  Pyramids.  In  like  manner,  we  infer  from 
the  phenomena  of  light  the  agency  of  waves,  because, 
as  far  as  our  experience  goes,  no  other  agency  could 
produce  the  phenomena. 

§  4»  The  Waves  of  Heat  which  produce  the  Vapour  of  our 
Atmosphere  and  melt  our  Glaciers. 

29.  Thus,  in  a  general  way,  I  have  given  you  the 
conception  and  the  grounds  of  the  conception,  which 
regards  light  as  the  product  of  wave-motion ;  but  we 
must  go  farther  than  this,  and  follow  the  conception  into 
some  of  its  details.  We  have  all  seen  the  waves  of 
water,  and  we  know  they  are  of  different  sizes — different 
in  length  and  different  in  height.  When,  therefore, 
you  are  told  that  the  atoms  of  the  sun,  and  of  almost 
all  other  luminous  bodies,  vibrate  at  different  rates,  and 
produce  waves  of  different  sizes,  your  experience  of 
water-waves  will  enable  you  to  form  a  tolerably  clear 
notion  of  what  is  meant. 


12  THE  FORMS  OF  WATER  IN 

30.  As  observed  above,  we  have  never  seen  the  light- 
waves, but  we  judge  of  their  presence,  their  position, 
and  their  magnitude,  by  their  effects.     Thei    lengths 
have  been  thus  determined,  and   found  to   vary  from 

about  To^Toth  to  6ooooth  of  an  incn- 

31.  But    besides    those   which   produce   light,    the 
sun  sends  forth  incessantly  a  multitude  of  waves  which 
produce  no  light.     The  largest  waves  which  the  sun 
sends  forth  are  of  this  non-luminous  character,  though 
they  possess  the  highest  heating  power. 

32.  A  common  sunbeam  contains  waves  of  all  kinds, 
but  it  is  possible  to  sift  or  filter  the  beam  so  as  to  inter- 
cept all  its  light,  and  to  allow  its  obscure  heat  to  pass 
unimpeded.      For    substances    have    been    discovered 
which,  while  intensely  opaque  to  the  light-waves,  are 
almost  perfectly  transparent  to  the  others.     On  the  other 
hand,  it  is  possible,  by  the  choice  of  proper  substances, 
to   intercept   in  a  great  degree  the  pure  heat-waves, 
and  to  allow  the   pure  light- waves  free  transmission. 
This  last  separation  is,  however,  not  so  perfect  as  the 
first. 

33.  We  shall  learn  presently  how  to  detach  the  one 
class  of  waves  from  the  other  class,  and  to  prove  that 
waves  competent  to  light  a  fire,  fuse  metal,  or  burn 
the  hand  like  a  hot  solid,  may  exist  in  a  perfectly  dark 
place. 

34.  Supposing,  then,  that  we  withdraw,  in  the  first 
instance   the  large   heat-waves,  and  allow  the  light- 


CLOUDS  AND  KIVERS,  ICE  AND  GLACIERS.  13 

waves  alone  to  pass.  These  may  be  concentrated  by 
suitable  lenses  and  sent  into  water  without  sensibly 
warming  it.  Let  the  light-waves  now  be  withdrawn, 
and  the  larger  heat-waves  concentrated  in  the  same 
manner ;  they  may  be  caused  to  boil  the  water  almost 
instantaneously. 

35.  This  is  the  point  to  which  I  wished  to  lead  you, 
and  which  without  due  preparation  could  not  be  under- 
stood.    You  now  perceive  the  important  part  played  by 
these  large  darkness- waves,  if  I  may  use  the  term,  in 
the  work  of  evaporation.     When  they  plunge  into  seas, 
lakes,  and  rivers,  they  are  intercepted  close  to  the  sur- 
face, and  they  heat  the   water   at  the   surface,  thus 
causing  it  to  evaporate ;  the  light-waves  at  the  same 
time  entering  to  great  depths  without  sensibly  heating 
the  water  through  which  they  pass.     Not  only,  there- 
fore, is  it  the  sun's  fire  which  produces  evaporation, 
but  a  particular  constituent  of  that  fire,  the  existence 
of  which  you  probably  were  not  aware  of. 

36.  Further,   it    is    these   selfsame   lightless   waves 
which,  falling  upon  the  glaciers  of  the  Alps,  melt  the 
ice  and  produce  all  the  rivers  flowing  from  the  glaciers ; 
for  I  shall  prove  to  you.  presently  that  the  light-waves, 
even  when  concentrated  to  the  uttermost,  are  unable 
to  melt  the  most  delicate  hoar-frost ;  much  less  would 
they  be  able  to  produce  the  copious  liquefaction  observed 
upon  the  glaciers. 

37.  These  large  lightless  waves  of  the  sun,  as  well  as 


14  THE  FOKMS  OE  WATER  IN 

the  heat-waves  issuing  from  non-luminous  hot  bodies, 
are  frequently  called  obscure  or  invisible  heat. 

We  have  here  an  example  of  the  manner  in  which 
phenomena,  apparently  remote,  are  connected  together 
in  this  wonderful  system  of  things  that  we  call  Nature. 
You. cannot  study  a  snow-flake  profoundly  without  being 
led  back  by  it  step  by  step  to  the  constitution  of  the  sun. 
It  is  thus  throughout  Nature.  All  its  parts  are  inter- 
dependent, and  the  study  of  any  one  part  completely 
would  really  involve  the  study  of  all. 

§  5.  Experiments  to  prove  the  foregoing  Statements. 

38.  Heat  issuing   from  any  source  not  visibly  red 
cannot  be  concentrated  so  as  to  produce  the  intense 
effects  just  referred  to.     To  produce  these  it  is  neces- 
sary to  employ  the  obscure  heat  of  a  body  raised  to  the 
highest  possible  state  of  incandescence.      The  sun  is 
such  a   body,  and  its  dark  heat  is  therefore  suitable 
for  experiments  of  this  nature. 

39.  But  in  the  atmosphere  of  London,  and  for  ex- 
periments such  as  ours,  the  heat-waves  emitted  by  coke 
raised  to  intense  whiteness  by  a  current  of  electricity 
are   much   more   manageable   than    the   sun's   waves. 
The  electric  light  has  also  the  advantage  that  its  dark 
radiation  embraces  a  larger  proportion  of  the  total  ra- 
diation than  the  dark  heat  of  the  sun.     In  fact,  the  force 
or  energy,  if  I  may  use  the  term,  of  the  dark  waves  of 
the  electric  light  is  fully  seven  times  that  of  its  light- 


CLOUDS  AND  EIVEES,  ICE  AND  GLACIEES.  15 

waves.     The  electric  light,  therefore,  shall  be  employed 
in  our  experimental  demonstrations. 

40.  From  this  source  a  powerful  beam  is  sent  through 
the  room,  revealing  its  track  by  the  motes  floating  in 
the  air  of  the  room ;  for  were  the  motes  entirely  absent 
the  beam  would  be  unseen.     It  falls  upon  a  concave 
mirror  (a   glass  one  silvered  behind  will  answer)  and 
is  gathered  up  by  the  mirror  into  a  cone  of  reflected 
rays  ;  the  luminous  apex  of  the  cone,  which  is  the  focus 
of  the  mirror,  being  about  fifteen  inches  distant  from  its 
reflecting  surface.     Let  us  mark  the  focus  accurately  by 
a  pointer. 

41.  And  now  let  us  place  in  the  path  of  the  beam  a 
substance  perfectly  opaque  to  light.     This  substance  is 
iodine  dissolved  in  a  liquid  called  bisulphide  of  carbon. 
The  light  at  the  focus  instantly  vanishes  when  the  dark 
solution  is  introduced.     But  the  solution  is   intensely 
transparent  to  the  dark  waves,  and  a  focus  of  such 
waves  remains  in  the  air  of  the  room  after  the  light 
has  been  abolished.     You  may  feel  the  heat  of  these 
waves  with  your  hand ;  you  may  let  them  fall  upon  a 
thermometer,  and  thus  prove  their  presence ;  or,  best 
of  all,  you  may  cause  them  to  produce  a  current  of 
electricity,  which  deflects  a  large  magnetic  needle.   The 
magnitude  of  the  deflection  is  a  measure  of  the  heat. 

42.  Our  object  now  is,  by  the  use  of  a  more  powerful 
lamp,   and    a  better    mirror    (one    silvered    in    front 
and  with   a   shorter   focal   distance),  to  intensify  the 


16  THE  FORMS  OF  WATER  IN 

action  liere  rendered  so  sensible.  As  before,  tlie  focus 
is  rendered  strikingly  visible  by  the  intense  illumina- 
tion of  the  dust  particles.  We  will  first  filter  the 
beam  so  as  to  intercept  its  dark  waves,  and  then  per- 
mit the  purely  luminous  waves  to  exert  their  utmost 
power  on  a  small  bundle  of  gun-cotton  placed  at  the 
focus. 

43.  No  effect  whatever  is  produced.     The  gun-cotton 
might  remain  there  for  a  week  without  ignition.     Let 
us   now  permit  the  unfiltered   beam  to  act  upon  the 
cotton.     It  is  instantly  dissipated  in  an  explosive  flash. 
This  experiment  proves  that  the  light-waves  are  incom- 
petent to  explode  the  cotton,  while  the  waves  of  the 
full  beam  are  competent  to  do  so  ;  hence  we  may  con- 
clude that  the  dark  waves  are  the  real  agents  in  the 
explosion. 

44.  But  this  conclusion  would  be  only  probable ;  for 
it  might  be  urged  that  the  mixture  of  the  dark  waves 
and  the  light- waves  is  necessary  to  produce  the  result. 
Let  us  then,  by  means  of  our  opaque  solution,  isolate 
our  dark  waves  and  converge  them  on  the  cotton.     It 
explodes  as  before. 

45.  Hence  it  is  the  dark  waves,  and  they  only,  that 
are  concerned  in  the  ignition  of  the  cotton. 

46.  At  the  same  dark  focus  sheets  of  platinum  are 
raised  to  vivid  redness ;   zinc  is  burnt  up ;  paper  in- 
stantly blazes ;  magnesium  wire  is  ignited ;    charcoal 
within  a  receiver  containing  oxygen  is  set  burning ;  a 


CLOUDS  AND  KIVERS,  ICE  AND  GLACIEES.  17 

diamond  similarly  placed  is  caused  to  glow  like  a  star, 
being  afterwards  gradually  dissipated.  And  all  this 
while  the  air  at  the  focus  remains  as  cool  as  in  any 
other  part  of  the  room. 

47.  To  obtain  the  light-waves   we  employ  a  clear 
solution  of  alum  in  water;  to  obtain  the  dark  waves 
we  employ  the  solution  of  iodine  above  referred  to. 
But  as  before  stated  (32),  the  alum  is  not  so  perfect  a 
filter  as  the  iodine ;  for  it  transmits  a  portion  of  the 
obscure  heat. 

48.  Though  the  light-waves  here  prove  their  incom- 
petence to  ignite  gun-cotton,  they  are  able  to  burn  up 
black  paper ;  or,  indeed,  to  explode  the  cotton  when  it 
is  blackened.     The  white  cotton  does  not  absorb  the 
light,  and  without  absorption  we  have  no  heating.    The 
blackened  cotton  absorbs,  is  heated,  and  explodes. 

49.  Instead  of  a  solution  of  alum,  we  will  employ  for 
our  next  experiment  a  cell  of  pure  water,  through  which 
the  light  passes  without  sensible  absorption.     At  the 
focus  is  placed  a  test-tube  also  containing  water,  the  full 
force  of   the  light  being  concentrated    upon  it.     The 
water  is  not  sensibly   warmed    by   the  concentrated 
waves.     We  now  remove  the  cell  of  water  ;  no  change 
is  visible  in  the  beam,  but  the  water  contained  in  the 
test-tube  now  boils. 

50.  The  light-waves  being  thus  proved  ineffectual, 
and  the  full  beam  effectual,  we  may  infer  that  it  is  the 
dark  waves  that  do  the  work  of  heating.  But  we  clenck 


18  THE  FOEMS   OF  WATER  IN 

our  inference  by  employing  our  opaque  iodine  filter 
Placing  it  on  the  path  of  the  beam,  the  light  is  entirely 
stopped,  but  the  water  boils  exactly  as  it  did  when  the 
full  beam  fell  upon  it. 

51.  The  truth  of  the  statement  made  in  paragraph  (34) 
is  thus  demonstrated. 

52.  And  now  with  regard  to  the  melting  of  ice.     On 
the  surface  of  a  flask  containing  a  freezing  mixture  we 
obtain  a  thick  fur  of  hoar-frost   (Par.  14).     Sending  the 
beam  through  a  water-cell,  its  luminous  waves  are  con- 
centrated upon  the  surface  of  the  flask.     Not  a  spicula 
of  the  frost  is  dissolved.    We  now  remove  the  water-cell, 
and  in  a  moment  a  patch  of  the  frozen  fur  as  large  as 
half-a-crown  is  melted.     Hence,  inasmuch  as  the  full 
beam  produces  this  effect,  and  the  luminous  part  of  the 
beam  does  not  produce  it,  we  fix  upon  the  dark  portion 
the  melting  of  the  frost. 

53.  As  before,  we  clench  this  inference  by  concentra- 
ting the  dark  waves  alone  upon  the  flask.     The  frost  is 
dissipated  exactly  as  it  was  by  the  full  beam. 

54.  These  effects  are  rendered  strikingly  visible  by 
darkening  with  ink  the  freezing  mixture  within  the 
flask.     When  the  hoar  frost  is  removed,  the  blackness 
of  the  surface  from  which  it  had  been  melted  comes 
out  in  strong  contrast  with  the  adjacent  snowy  white- 
ness.    When  the  flask  itself,  instead  of  the  freezing 
mixture,  is  blackened,  the  purely  luminous  waves  being 
absorbed  by  the  glass,  warm  it ;  the  glass  reacts  upon 


CLOUDS  AND  EIVEKS,   ICE  AND  GLACIERS.  19 

the  frost,  and  melts  it.    Hence  the  wisdom  of  darkening, 
instead  of  the  flask  itself,  the  mixture  within  the  flask. 

55.  This   experiment   proves    to   demonstration  the 
statement  in  paragraph  (36) :  that  it  is  the  dark  waves 
of  the  sun  that  melt  the  mountain  snow  and  ice,  and 
originate  all  the  rivers  derived  from  glaciers. 

There  are  writers  who  seem  to  regard  science  as  an 
aggregate  of  facts,  and  hence  doubt  its  efficacy  as  an 
exercise  of  the  reasoning  powers.  But  all  that  I  have 
here  taught  you  is  the  result  of  reason,  taking  its  stand, 
however,  upon  the  sure  basis  of  observation  and  experi- 
ment. And  this  is  the  spirit  in  which  our  further 
studies  are  to  be  pursued. 

§  6.  Oceanic  Distillation. 

56.  The  sun,  you  know,  is  never  exactly  overhead  in 
England.     But  at  the  equator,  and  within  certain  li- 
mits north  and  south  of  it,  the  sun  at  certain  periods  of 
the  year  is  directly  overhead  at  noon.    These  limits  are 
called  the  Tropics  of  Cancer  and  of  Capricorn.    Upon 
the  belt  comprised  between  these  two  circles  the  sun's 
rays  fall  with   their  mightiest   power ;  for  here  they 
shoot  directly  downwards,  and  heat  both  earth  and  sea 
more  than  when  they  strike  slantingly. 

57.  When  the  vertical  sunbeams  strike  the  land  they 
heat  it,  and  the  air  in  contact  with  the  hot  soil  becomes 
heated  in  turn.     But  when  heated  the  air  expands,  and 
when  it  expands  it  becomes  lighter.     This  lighter  air 


20  THE  FOSMk  OF  WATER  IN 

rises,  like  wood  plunged  into  water,  through  the  heavier 
air  overhead. 

58.  When  the  sunbeams  fall  upon  the  sea  the  water 
is   warmed,  though  not   so   much   as   the   land.     The 
warmed  water  expands,  becomes  thereby  lighter,  and 
therefore  continues  to  float  upon  the  top.     This  upper 
layer  of  water  warms  to  some  extent  the  air  in  contact 
with  it,  but  it  also  sends  up   a  quantity   of  aqueous 
vapour,  which   being   far  lighter  than  air,  helps   the 
latter  to  rise.     Thus  both  from  the  land  and  from  the 
sea  we  have   ascending   currents   established  by  the 
action  of  the  sun. 

59.  When   they  reach   a  certain  elevation   in  the 
atmosphere,    these    currents    divide    and    flow,    part 
towards  the  north  and  part  towards  the  south;  while 
from  the  north  and  the  south  a  flow  of  heavier  and 
colder  air  sets  in  to  supply  the  place  of  the  ascending 
warm  air. 

60.  Incessant  circulation  is  thus  established  in  the 
atmosphere.     The  equatorial  air  and  vapour  flow  above 
towards  the  north  and  south  poles,  while  the  polar  air 
flows  below  towards  the  equator.     The  two  currents  of 
air  thus  established  are  called  the  upper  and  the  lower 
trade  winds. 

61.  But  before  the  air  returns  from  the  poles  great 
changes  have  occurred.     Tor  the  air  as  it  quitted  the 
equatorial  regions   was   laden    with   aqueous   vapour, 
which  could  not  subsist  in  the  cold  polar  regions.     It  is 


CLCUDS  AND  RIVERS,  ICE  AND   GLACIERS.  21 

there  precipitated,  falling  sometimes  as  rain,  or  more 
commonly  as  snow.  The  land  near  the  pole  is  covered 
with  this  snow,  which  gives  birth  to  vast  glaciers  in  a 
manner  hereafter  to  be  explained. 

62.  It  is  necessary  that  you  should  have  a  perfectly 
clear  view  of  this  process,  for  great  mistakes  have  been 
made  regarding  the  manner  in  w.hich  glaciers  are  related 
to  the  heat  of  the  sun. 

63.  It  was  supposed  that   if  the   sun's   heat  were 
diminished,  greater  glaciers  than   those  now  existing 
would  be  produced.     But  the  lessening   of  the   sun's 
heat  would  infallibly  diminish  the  quantity  of  aqueous 
vapour,  and  thus  cut  off  the  glaciers  at  their  source. 
A  brief  illustration  will  complete  your  knowledge  here. 

64.  In  the  process  of  ordinary  distillation,  the  liquid 
to  be  distilled  is  heated  and  converted  into  vapour  in 
one  vessel,  and  chilled  and  reconverted  into  liquid  in 
another.     What  has  just  been  stated  renders  it  plain 
that  the  earth  and  its  atmosphere  constitute  a  vast  dis- 
tilling apparatus  in  which  the  equatorial  ocean  plays 
the  part  of  the  boiler,  and  the  chill  regions  of  the  poles 
the  part  of  the  condenser.     In  this  process  of  distilla- 
tion heat  plays  quite  as  necessary  a  part  as  cold,  and 
before  Bishop  Heber  could  speak  of  *  Greenland's  icy 
mountains,'  the  equatorial  ocean  had  to  be  warmed  by 
the  sun.     We  shall  have  more  to  say  upon  this  question 
afterwards. 


22  THE  FOKMS  OP  WATEE  IN 


ILLUSTRATIVE  EXPERIMENTS. 

65.  I  have  said  that  when  heated,  air  expands.     If 
you  wish  to  verify  this  for  yourself,  proceed  thus.    Take 
an  empty  flask,  stop  it  by  a  cork ;  pass  through  the  cork 
a  narrow  glass  tube.     By  heating  the  tube  in  a  spirit- 
lamp   you  can  bend  it  downwards,  so  that  when  the 
flask  is  standing  upright  the  open  end  of  the  narrow 
tube  may  dip  into  water.     Now  cause   the   flame   of 
your  spirit-lamp  to  play  against  the  flask.     The  flame 
heats  the  glass,  the  glass  heats  the  air ;    the  air  ex- 
pands, is   driven  through  the  narrow  tube,  and  issues 
in  a  storm  of  bubbles  from  the  water. 

66.  Were  the  heated  air  unconfmed,  it  would  rise  in 
the  heavier  cold  air.     Allow  a  sunbeam  or   any  other 
intense  light  to  fall  upon  a  white  wall  or  screen  in  a  dark 
room.     Bring  a  heated  poker,  a  candle,  or  a  gas  flame 
underneath  the  beam.     An  ascending  current  rises  from, 
the  heated  body  through  the   beam,  and  the   action 
of  the   air  upon  the   light  is  such   as  to  render  the 
wreathing  and  waving  of  the  current  strikingly  visible 
upon  the  screen.    When  the  air  is  hot  enough,  and  there- 
fore light  enough,  if  entrapped  in  a  paper  bag  it  carries 
the  bag  upwards,  and  you  have  the  Fire -balloon. 

.  67.  Fold  two  sheets  of  paper  into  two  cones  and 
suspend  them,  with  their  closed  points  upwards  from 
the  end  of  a  delicate  balance.  See  that  the  cones 


CLOUDS  AND  RIVERS,  ICE  AND   GLACIERS.  23 

balance  each,  other.  Then  place  for  a  moment  the 
flame  of  a  spirit-lamp  beneath  the  open  base  of  one  of 
them  ;  the  hot  air  ascends  from  the  lamp  and  instantly 
tosses  upwards  the  cone  above  it. 

68.  Into  an  inverted  glass  shade  introduce   a  little 
smoke.     Let   the  air   come   to  rest,   and  then  simply 
place  your  hand   at   the   open   mouth   of  the    shade. 
Mimic  hurricanes  are  produced  by  the  air  warmed  by 
the  hand,  which  are  strikingly  visible  when  the  smoke 
is  illuminated  by  a  strong  light. 

69.  The   heating  of  the  tropical  air  by  the  sun  is 
indirect.     The  solar  beams  have  scarcely  any  power  to 
heat  the  air  through  which  they  pass ;   but  they  heat 
the  land  and  ocean,  and  these  communicate  their  heat 
to  the  air  in  contact  with  them.     The  air  and  vapour 
start  upwards  charged  with  the  heat  thus  communi- 
cated. 

§  7.   Tropical  Rains. 

70.  But  long  before  the    air  and  vapour  from  the 
equator  reach  the  poles,  precipitation  occurs.    Wherever 
a  humid  warm  wind  mixes  with  a  cold  dry  one,  rain 
falls.     Indeed  the  heaviest  rains  occur  at  those  places 
where  the  sun  is  vertically  overhead.     We  must  enquire 
a  little  more  closely  into  their  origin. 

71.  Fill  a  bladder  about  two-thirds  full  of  air  at  the 
sea  level,  and  take  it  to  the  summit  of  Mont  Blanc.     As 
you  ascend,  the  bladder  becomes  more  and  more  dis- 


24  THE  FOKMS  OF  WATEE  IN 

tended;  at  the  top  of  the  mountain  it  is  fully  distended, 
and  has  evidently  to  bear  a  pressure  from,  within. 
Returning  to  the  sea  level  you  find  that  the  tightness 
disappears,  the  bladder  finally  appearing  as  flaccid  as 
at  first. 

72.  The  reason  is  plain.     At  the  sea  level  the  air 
within  the  bladder  has   to   bear  the  pressure   of  the 
whole  atmosphere,  being  thereby  squeezed  into  a  com- 
paratively small  volume.     In  ascending  the  mountain, 
you  leave  more  and  more  of  the   atmosphere  behind ; 
the  pressure  becomes  less  and  less,  and  by  its  expansive 
force  the  air  within  the  bladder  swells  as  the  outside 
pressure  is  diminished.     At  the  top  of  the  mountain 
the  expansion  is  quite  sufficient  to  render  the  bladder 
tight,  the  pressure  within  being  then  actually  greater 
than  the  pressure  without.     By  means  of  an  air-pump 
we  can  show  the  expansion  of  a  balloon  partly  filled 
with  air,  when  the  external  pressure  has  been  in  part 
removed. 

73.  But  why  do  I  dwell  upon  this  ?     Simply  to  make 
plain  to  you  that  the  unconfined  air,  heated  at  the  earth's 
surface,  and  ascending  by  its  lightness,  must  expand 
more  and  more  the  higher  it  rises  in  the  atmosphere. 

74.  And  now  I  have  to  introduce  to  you  a  new  fact, 
towards  the  statement  of  which  I  have  been  working 
for  some  time.     II  is  this : — The  ascending  air  is  chilled 
by  its  expansion.     Indeed  this  chilling  is  one  source  of 
the  coldness  of  the  higher  atmospheric  regions.     And 


CLOUDS  AND  KIVEES,   ICE  AND   GLACIERS.  25 

now  fix  your  eye  upon  those  mixed  currents  of  air  and 
aqueous  vapour  which  rise  from  the  warm  tropical  ocean. 
They  start  with  plenty  of  heat  to  preserve  the' vapour 
as  vapour;  but  as  they  rise  they  come  into  regions 
already  chilled,  and  they  are  still  further  chilled  by 
their  own  expansion.  The  consequence  might  be  fore- 
seen. The  load  of  vapour  is  in  great  part  precipitated, 
dense  clouds  are  formed,  their  particles  coalesce  to 
rain-drops,  which  descend  daily  in  gushes  so  profuse 
that  the  word  'torrential'  is  used  to  express  the 
copiousness  of  the  rain-fall.  I  could  show  you  this 
chilling  by  expansion,  and  also  the  consequent  precipi- 
tation of  clouds. 

75.  Thus  long  before  the  air  from  the  equator  reaches 
the  poles  its  vapour  is  in  great  part  removed  from  it, 
having  redescended  to  the  earth  as  rain.     Still  a  good 
quantity  of  the  vapour  is  carried  forward,  which  yields 
hail,  rain,  and  snow  in  northern  and  southern  lands. 

ILLUSTRATIVE  EXPEKIMENTS. 

76.  I  have  said  that  the  air  is  chilled  during  its  ex- 
pansion.    Prove  this,  if  you  like,  thus.     With  a  con- 
densing syringe,  you  can  force  air  into  an  iron  box 
furnished  with  a   stopcock,  to  which  the    syringe   is 
screwed.     Do  so  till  the  density  of  the  air  within  the 
box  is  doubled  or  trebled.     Immediately  after  this  con- 
densation, both  the  box  and  the  air  within  it  are  warm, 
and  can  be  proved  to  be  so  by  a  proper  thermometer. 


26  THE  FOKMS  OF  WATEK  IN 

Simply  turn  the  cock  and  allow  the  compressed  air  to 
stream  into  the  atmosphere.  The  current,  if  allowed  to 
strike  a  thermometer,  visibly  chills  it;  and  with  other 
instruments  the  chill  may  be  made  more  evident  still. 
Even  the  hand  feels  the  chill  of  the  expanding  air. 

77.  Throw  a  strong  light,  a  concentrated  sunbeam  for 
example,  across  the  issuing  current ;  if  the  compressed 
air  be  ordinary  humid  air,  you  see  the  precipitation  of  a 
little  cloud  by  the  chill  accompanying  the  expansion. 
This  cloud-formation  may,  however,  be  better  illustrated 
in  the  following  way  : — 

78.  In  a  darkened  room  send  a  strong  beam  of  light 
through  a  glass  tube  three  feet  long  and  three  inches 
wide,  stopped  at  its  ends  by  glass  plates.     Connect  the 
tube  by  means  of  a  stopcock  with  a  vessel  of  about  one- 
fourth  its  capacity,  from  which  the  air  has  been   re- 
moved by  an  air-pump.    The  exhausted  cylinder  of  the 
pump  itself  will  answer  capitally.     Fill  the  glass  tube 
with  humid   air ;   then  simply  turn  on  the   stopcock 
which  connects  it  with  the  exhausted  vessel.     Having 
more  room  the  air  expands,  cold  accompanies  the  ex- 
pansion, and,  as  a  consequence,  a  dense  and  brilliant 
cloud  immediately  fills  the  tube.     If  the  experiment  be 
made  for  yourself  alone  you  may  see  the  cloud  in  ordi- 
nary  daylight;  indeed,  the   brisk  exhaustion   of  any 
receiver  filled  with  humid  air  is  known  to  produce  this 
condensation. 

79.  Other  vapours  than  that  of  water  may  be  thus 


CLOUDS  AND  KIVERS,   ICE  AND  GLACIERS.  27 

precipitated,  some  of  them  yielding  clouds  of  intense 
brilliancy,  and  displaying  iridescences,  such  as  are  some- 
times, but  not  frequently,  seen  in  the  clouds  floating 
over  the  Alps. 

80.  In  science  what  is  true  for  the  small  is  true  for 
the  large.     Thus  by  combining  the  conditions  observed 
on  a  large  scale  in  nature  we  obtain  on  a  small  scale  the 
phenomena  of  atmospheric  clouds. 

§  8.  Mountain  Condensers. 

81.  To  complete  our  view  of  the  process  of  atmo- 
spheric precipitation  we  must  take  into   account  the 
action  of  mountains.      Imagine    a    south-west   wind 
blowing   across  the  Atlantic  towards  Ireland.     In  its 
passage  it  charges  itself  with  aqueous  vapour.     In  the 
south  of  Ireland  it  encounters  the  mountains  of  Kerry : 
the   highest   of  these   is   Magillicuddy's   Reeks,   near 
Killarney.     Now  the  lowest  stratum  of  this  Atlantic 
wind  is  that  which  is  most  fully  charged  with  vapour. 
When  it  encounters  the  base  of  the  Kerry  mountains 
it  is  tilted  up  and  flows  bodily  over  them.     Its  load -of 
vapour  is  therefore  carried  to  a  height,  it  expands  on 
reaching  the  height,  it  is  chilled  in  consequence  of  the 
expansion,  and  comes  down  in  copious  showers  of  rain. 
From  this,  in  fact,  arises  the  luxuriant  vegetation  of 
Killarney;  to  this,  indeed,  the  lakes  owe  their  water 
supply.     The  cold  crests  of  the  mountains  also  aid  in 
the  work  of  condensation. 


28  THE  FOKMS  OF  WATEK  IN 

82.  Note  the  consequence.     There  is  a  town  called 
Cahirciveen  to  the  south-west  of  Magillicuddy's  Keeks, 
at  which  observations  of  the  rainfall  have  been  made, 
and  a  good  distance  farther  to  the  north-east,  right  in 
the  course  of  the  south-west  wind,  there  is  another  town, 
called  Portarlington,  at  which  observations  of  rainfall 
have  also  been  made.     But  before  the  wind  reaches  the 
latter  station  it  has  passed  over  the  mountains  of  Kerry 
and  left  a   great  portion   of  its  moisture   behind   it. 
What   is   the   result?     At   Cahirciveen,  as   shown  by 
Dr.  Lloyd,  the  rainfall  amounts  to  59  inches  in  a  year, 
while  at  Portarlington  it  is  only  21  inches. 

83.  Again,  you   may   sometimes   descend   from  the 
Alps  when  the  fall  of  rain  and  snow  is  heavy  and  in- 
cessant, into  Italy,  and  find  the  sky  over  the  plains  of 
Lombardy  blue  and  cloudless,  the  wind  at  the   same 
time  blowing  over   the  plain  towards  the  Alps.     Below 
the  wind  is  hot  enough  to  keep  its  vapour  in  a  perfectly 
transparent  state ;  but  it  meets  the  mountains,  is  tilted 
up,  expanded,  and  chilled.     The   cold   of  the   higher 
summits  also  helps  the  chill.     The  consequence  is  that 
the  vapour  is  precipitated  as  rain  or  snow,  thus  producing 
bad  weather  upon  the  heights,  while  the  plains  below, 
flooded  with  the  same  air,  enjoy  the  aspect  of  the  un- 
clouded summer  sun.    Clouds  blowing  from  the  Alps  are 
also  sometimes  dissolved  over  the  plains  of  Lombardy. 

84.  In  connection  with  the  formation  of  clouds  by 
mountains,  one  particularly  instructive  effect  may  be 


CLOUDS  AND  EIVERS,  ICE  AXD   GLACIERS.  29 

here  noticed.  You  frequently  see  a  streamer  of  cloud 
many  hundred  yards  in  length  drawn  out  from  an 
Alpine  peak.  Its  steadiness  appears  perfect,  though  a 
strong  wind  may  be  blowing  at  the  same  time  over  the 
mountain  head.  Why  is  the  cloud  not  blown  away? 
It  is  blown  away  ;  its  permanence  is  only  apparent.  At 
one  end  it  is  incessantly  dissolved,  at  the  other  end  it 
is  incessantly  renewed  :  supply  and  consumption  being 
thus  equalized,  the  cloud  appears  as  changeless  as  the 
mountain  to  which  it  seems  to  cling.  When  the  red 
sun  of  the  evening  shines  upon  these  cloud-streamers 
they  resemble  vast  torches  with  their  flames  blown 
through  the  air. 

§  9.  Architecture  of  Snow. 

85.  We  now  resemble  persons  who  have  climbed  a 
difficult  peak,  and  thereby  earned  the  enjoyment  of  a 
wide  prospect.     Having  made  ourselves  masters  of  the 
conditions  necessary  to  the   production   of  mountain 
snow,  we  are  able  to  take  a  comprehensive  and  intelli- 
gent view  of  the  phenomena  of  glaciers. 

86.  A  few  words  are  still  necessary  as  to  the  forma- 
tion of  snow.     The  molecules  and  atoms  of  all  sub- 
stances, when  allowed  free  play,  build  themselves  into 
definite  and,  for  the  most  part,  beautiful  forms  called 
crystals.     Iron,  copper,  gold,  silver,  lead,  sulphur,  when 
melted  and  permitted  to  cool  gradually,  all  show  this 
crystallizing  power.     The  metal  bismuth  shows  it  in  a 


30  THE  FOKMS   OF  WATEK  IN 

particularly  striking  manner,  and  when  properly  fused 
and  solidified,  self-built  crystals  of  great  size  and  beauty 
are  formed  of  this  metal. 

87.  If  you  dissolve  saltpetre  in  water,  and  allow  the 
solution   to   evaporate  slowly,   you  may   obtain   large, 
crystals,  for  no  portion  of  the  salt   is  converted  into 
vapour.   The  water  of  our  atmosphere  is  fresh  though  it 
is  derived  from  the  salt  sea.     Sugar  dissolved  in  water, 
and  permitted  to  evaporate,  yields  crystals  of  sugar- 
candy.     Alum   readily   crystallizes   in   the    same  way. 
Flints  dissolved,  as  they  sometimes  are  in  nature,  and 
permitted  to  crystallize,  yield  the  prisms  and  pyramids 
of  rock  crystal.     Chalk  dissolved  and  crystallized  yields 
Iceland  spar.     The  diamond  is  crystallized  carbon.     All 
our  precious  stones,  the  ruby,  sapphire,  beryl,  topaz, 
emerald,  are  all  examples  of  this  crystallizing  power. 

88.  You  have  heard  of  the  force  of  gravitation,  and 
you  know  that   it  consists   of  an  attraction  of  every 
particle  of  matter  for  every  other  particle.     You  know 
that  planets  and  moons  are  held  in  their  orbits  by  this 
attraction.     But  gravitation  is  a  very  simple  affair  com- 
pared to  the  force,  or  rather  forces,  of  crystallization. 
For  here  the  ultimate  particles  of  matter,  inconceivably 
small  as  they  are,  show  themselves  possessed  of  attrac- 
tive and  repellent  poles,  by  the  mutual  action  of  which 
the  shape  and  structure  of  the  crystal  are  determined. 
In  the  solid  condition  the  attracting  poles  are  rigidly 
locked  together;  but  if  sufficient  heat  be  applied  the 


CLOUDS  AND  KIVEES,  ICE  AND  GLACIEES.  31 

bond  of  union  is  dissolved,  and  in  the  state  of  fusion  the 
poles  are  pushed  so  far  asunder  as  to  be  practically  out  of 
each  other's  range.  The  natural  tendency  of  the  mole- 
cules to  build  themselves  together  is  thus  neutralized. 

89.  This  is  the  case  with  water,  which  as  a  liquid  is 
to   all  appearance  formless.     When  sufficiently  cooled 
the   molecules   are   brought  within  the   play   of   the 
crystallizing  force,  and  they  then  arrange  themselves  in 
forms  of  indescribable  beauty.     When  snow  is  produced 
in   calm   air,  the   icy  particles   build  themselves  into 
beautiful  stellar  shapes,  each  star  possessing  six  rays. 
There  is  no  deviation  from  this  type,  though  in  other 
respects  the  appearances  of  the  snow-stars  are  infinitely 
various.     In  the  polar  regions   these   exquisite  forms 
were   observed  by  Dr.  Scoresby,  who  gave   numerous 
drawings  of  them.     I  have  observed  them  in  mid- winter 
filling  the  air,  and  loading  the  slopes  of  the  Alps.     But 
in  England  they  are  also  to  be  seen,  and  no  words  of 
mine   could   convey  so   vivid   an   impression   of  their 
beauty   as   the   annexed  drawings  of  a  few  of  them, 
executed  at  Greenwich  by  Mr.  Glaisher. 

90.  It  is   worth  pausing  to   think   what  wonderful 
work  is  going  on  in  the  atmosphere  during  the  forma- 
tion and  descent  of  every  snow-shower :  what  building 
power  is  brought  into  play !  and  how  imperfect  seem 
the  productions  of  human  minds  and  hands  when  com- 
pared with  those  formed  by  the  blind  forces  of  nature  ! 

91.  But  who  ventures  to  call  the  forces  of  nature 


32      THE  FORMS   OF  WATER  IN  CLOUDS,  RIVERS,  ETC. 

blind  ?  In  reality,  when  we  speak  thus  we  are  describing 
our  own  condition.  The  blindness  is  ours ;  and  what 
we  really  ought  to  say,  and  to  confess,  is  that  our  powers 
are  absolutely  unable  to  comprehend  either  the  origin 
or  the  end  of  the  operations  of  nature. 

92.  But  while  we  thus  acknowledge  our  limits,  there 
is  also  reason  for  wonder  at  the  extent  to  which  science 
has  mastered  the  system  of  nature.     From  age  to  age, 
and  from  generation  to  generation,  fact  has  been  added 
to  fact,  and  law  to  law,  the  true  method  and  order  of 
the  Universe  being  thereby  more  and  more  revealed. 
In  doing  this  science  has  encountered  and  overthrown 
various  forms  of  superstition  and  deceit,  of  credulity 
and  imposture.     But   the  world   continually  produces 
weak  persons  and  wicked  persons ;  and  as  long  as  they 
continue  to  exist  side  by  side,  as  they  do  in  this  our 
day,  very  debasing  beliefs  will  also  continue  to  infest 
the  world. 

§  10.  Atomic  Poles. 

93.  'What  did  I  mean  when,  a  few  moments  ago 
(88),  I  spoke  of  attracting  and  repellent  poles  ? '     Let 
me  try  to  answer  this  question.     You  know  that  astro- 
nomers and  geographers  speak  of  the  earth's  poles,  and 
you  have  also  heard  of  magnetic  poles,  the  poles  of  a 
magnet  being  the  points  at  which  the  attraction  and 
repulsion  of  the  magnet  are  as  it  were  concentrated. 

94.  Every  magnet  possesses  two  such  poles ;  and  if 


BNOTV  CRTSTAM. 


34  THE  FOEMS   OF  WATER  IN 

iron  filings  be  scattered  over  a  magnet,  each  particle 
becomes  also  endowed  with  two  poles.  Suppose  such 
particles  devoid  of  weight  and  floating  in  our  atmosphere, 
what  must  occur  when  they  come  near  each  other? 
Manifestly  the  repellent  poles  will  retreat  from  each 
other,  while  the  attractive  poles  will  approach  and 
finally  lock  themselves  together.  And  supposing  the 
particles,  instead  of  a  single  pair,  to  possess  several  pairs 
of  poles  arranged  at  definite  points  over  their  surfaces ; 
you  can  then  picture  them,  in  obedience  to  their  mutual 
attractions  and  repulsions,  building  themselves  together 
to  form  masses  of  definite  shape  and  structure. 

95.  Imagine  the  molecules  of  water  in  calm  cold  air  to 
be  gifted  with  poles  of  this  description,  which  compel  the 
particles  to  lay  themselves  together  in  a  definite  order, 
and  you  have  before  your  mind's  eye  the  unseen  archi- 
tecture which  finally  produces  the  visible  and  beautiful 
crystals  of  the  snow.  Thus  our  first  notions  and  con- 
ceptions of  poles  are  obtained  from  the  sight  of  our 
eyes  in  looking  at  the  effects  of  magnetism ;  and  we 
then  transfer  the.«e  notions  and  conceptions  to  particles 
which  no  eye  has  ever  seen.  The  power  by  which  we 
thus  picture  to  ourselves  effects  beyond  the  range  of  the 
senses  is  what  philosophers  call  the  Imagination,  and 
in  the  effort  of  the  mind  to  seize  upon  the  unseen 
architecture  of  crystals,  we  have  an  example  of  the 
'  scientific  use '  of  this  faculty.  Without  imagination 
we  might  have  critical  power,  but  not  creative  power  in 
science. 


CLOUDS  AND  RIVERS,  ICE  AND   GLACIERS.  35 


§11.  Architecture  of  LaJce  Ice. 

96.  We  have  thus  made  ourselves  acquainted  with 
the    beautiful    snow-flowers    self-constructed    by   the 
molecules  of  water  in  calm  cold  air.      Do  the  mole- 
cules  show    this    architectural   power   when   ordinary 
water  is  frozen  ?     What,  for  example,  is  the  structure 
of  the  ice  over  which  we  skate  in  winter  ?     Quite  as 
wonderful  as  the  flowers  of  the  snow.     The  observation 
is   rare,  if  not  new,  but  I  have  seen  in  water  slowly 
freezing  six-rayed  ice-stars  formed,  and  floating  free 
on  the  surface.     A  six-rayed  star,  moreover,  is  typical 
of  the  construction  of  all  our  lake  ice.     It  is  built  up 
of  such  forms  wonderfully  interlaced. 

97.  Take  a  slab  of  lake  ice  and  place  it  in  the  path 
of  a  concentrated  sunbeam.     Watch  the  track  of  the 
beam  through  the  ice.     Part  of  the  beam  is  stopped, 
part  of  it  goes  through ;  the  former  produces  internal 
liquefaction,  the  latter  has  no  effect  whatever  upon  the 
ice.     But  the  liquefaction   is  not  uniformly   diffused. 
From  separate  spots  of  the  ice  little  shining  points  are 
seen  to  sparkle  forth.     Every  one  of  those  points  is  sur- 
rounded by  a  beautiful  liquid  flower  with  six  petals. 

98.  Ice  and  water  are  so  optically  alike  that  unless 
the  light  fall  properly  upon  these  flowers  you  cannot 
see  them.     But  what  is  the  central  spot  ?     A  vacuum. 
Ice  swims  on  water  because,  bulk  for  bulk,  it  is  lighter 


36  THE  FOEMS  OF  WATEE  IN 

than  water ;  so  that  when  ice  is  melted  it  shrinks  in 
size.  Can  the  liquid  flowers  then  occupy  the  whole 
space  of  the  ice  melted?  Plainly  no.  A  little  empty 
space  is  formed  with  the  flowers,  and  this  space,  or 
rather  its  surface,  shines  in  the  sun  with  the  lustre  of 
burnished  silver. 

99.  In  all  cases  the  flowers  are  formed  parallel  to 
the  surface  of  freezing.     They  are  formed  when  the 
sun  shines  upon  the  ice  of  every  lake;  sometimes  in 
myriads,  and  so  small  as  to  require  a  magnifying  glass 
to  see  them.      They  a-re   always  attainable,  but  their 
beauty  is  often  marred  by  internal  defects  of  the  ice. 
Even  one  portion  of  the  same  piece  of  ice  may  show 
them  exquisitely,  while  a  second  portion  shows  them 
imperfectly. 

100.  Annexed  is  a  very  imperfect   sketch  of  these 
beautiful  figures. 

101.  Here  we   have   a  reversal   of   the   process   of 
crystallization.      The  searching  solar  beam  is  delicate 
enough  to  take  the  molecules  down  without  deranging 
the  order  of  their  architecture.     Try  the  experiment  for 
yourself  with  a  pocket-lens  on  a  sunny  day.     You  will 
not  find  the  flowers  confused ;   they  all  lie  parallel  to 
the  surface  of  freezing.     In  this  exquisite  way  every 
bit  of  the  ice  over  which  our  skaters  glide  in  winter  is 
put  together. 

102.  I  said  in  (97)  that  a  portion  of  the  sunbeam  was 
stopped  by   the   ice  and  liquefied  it.     What  is   this 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS. 


37 


portion  9     The  dark  heat  of  the  sun.     The  great  body 
of  the  light  waves  and  even  a  portion  of  the  dark  ones, 


LIQUID  FLOWERS   IN  LAKE  ICE. 


pass  through  the  ice  without  losing  any  of  their  heating 
power.  When  properly  concentrated  on  combustible 
bodies,  even  after  having  passed  through  the  ice,  their 
burning  power  becomes  manifest. 

103.  And   the  ice  itself  may  be  employed  to  con- 
centrate them.     With  an  ice-lens  in  the  polar  regions 
Dr.  Scoresby  has  often  concentrated  the  sun's  rays  so 
as  to  make  them  burn  wood,  fire  gunpowder,  and  melt 
lead ;  thus  proving  that  the  heating  power  is  retained 
by  the  rays,  even  after  they  have  passed  through  so  cold 
a  substance. 

104.  By   rendering   the   rays   of  the   electric   lamp 
parallel,  and  then  sending  them  through  a  lens  of  ice, 
we  obtain  all  the  effects  which  Dr.  Scoresby  obtained 
with  the  rays  of  the  sun. 


88  THE  FOKMS   OF  WATER  IN 


§12.  The  Source  of  the  Arveiron.     Ice  Pinnacles,  Towers^ 

and  Chasms  of  the  Glacier  des  Bois.    Passage 

to  the  Montanvert. 

105.  Our   preparatory  studies   are   for  the  present 
ended,  and  thus  informed,  let  us  approach  the  Alps. 
Through   the  village   of  Chamouni,  in  Savoy,  a  river 
rushes  which  is   called   the   Arve.     Let  us  trace  this 
river  backwards  from  Chamouni.     At  a  little  distance 
from  the  village  the  river  forks  ;  one  of  its  branches  still 
continues  to  be  called  the  Arve,  the  other  is  the  Arvei- 
ron.    Following  this  latter  we  come  to  what  is  called 
the  '  source  of  the  Arveiron  ' — a  short  hour's  walk  from 
Chamouni.     Here,  as  in  the  case  of  the  Rhone  already 
referred  to,  you  are  fronted  by  a  huge  mass  of  ice,  the 
end  of  a  glacier,  and  from  an  arch  in  the  ice  the  Ar- 
veiron issues.     Do  not  trust  the  arch  in  summer.     Its 
roof  falls  at  intervals  with  a  startling  crash,  and  would 
infallibly  crush  any  person  on  whom  it  might  fall. 

106.  We  must  now  be  observant.     Looking  about  us 
here,  we  find  in  front  of  the  ice  curious  heaps  and  ridges 
of  debris,  which  are  more  or  less  concentric.     These  are 
the  terminal  moraines  of  the  glacier.     We  shall  examine 
them  subsequently. 

107.  We  now  turn  to  the  left,  and  ascend  the  slope 
beside  the  glacier.     As  we  ascend  we  get  a  better  view, 
and  find  that  the  ice  here  fills  a  narrow  valley.     We 


CLOUDS  AND  RIVERS,   ICE  AND   GLACIERS. 


39 


come  upon  another  singular  ridge,  not  of  fresh  debris, 
like  those  lower  down,  but  covered  in  part  with  trees, 
and  appearing  to  be  literally  as  '  old  as  the  hills.'  It 
tells  a  wonderful  tale.  We  soon  satisfy  ourselves  that 
the  ridge  is  an  ancient  moraine,  and  at  once  conclude 
that  the  glacier,  at  some  former  period  of  its  existence, 


SOURCE    OF  THE  ARVEIROX. 


was  vastly  larger  than  it  is  now.  This  old  moraine 
stretches  right  across  the  main  valley,  and  abuts  against 
the  mountains  at  the  opposite  side. 

108.  Having  passed  the  terminal  portion  of  the 
glacier,  which  is  covered  with  stones  and  rubbish,  we 
find  ourselves  beside  a  very  wonderful  exhibition  of  ice. 


40 


THE  FORMS  OF  WATER  IN 


The  glacier  descends  a  steep  gorge,  and  in  doing  so  is 
riven  and  broken  in  the  most  extraordinary  manner. 
Here  are  towers,  and  pinnacles,  and  fantastic  shapes 
wrought  out  by  the  action  of  the  weather,  which  put 
one  in  mind  of  rude  sculpture.  Annexed  is  a  sketch 
of  an  ice-pinnacle.  From  deep  chasms  in  the  glacier 


ICE-PINNACLE. 


issues  a  delicate  shimmer  of  blue  light.  At  times  we 
hear  a  sound  like  thunder,  which  arises  either  from 
the  falling  of  a  tower  of  ice,  or  from  the  tumble  of  a 
huge  stone  into  a  chasm.  The  glacier  maintains  this 
wild  and  chaotic  character  for  some  time ;  and  the  best 


CLOUDS  AND  EIVEES,  ICE  AND  GLACISES.  41 

iceman  would  find  himself  defeated  in  any  attempt  to 
get  along  it. 

109.  We  reach  a  place  called  the  Chapeau,  where,  if 
we  wish,  we  can  have  refreshment  in  a  little  mountain 
hut.     We  then  pass  the  Mauvais  Pas,  a  precipitous 
rock,  on  the  face  of  which  steps  are  hewn,  and  the  un- 
practised traveller  is  assisted  by  a  rope.     We  pursue 
our  journey,  partly  along  the  mountain  side,  and  partly 
along  a  ridge  of  singularly  artificial  aspect — a  lateral 
moraine.     We  at  length  face  a  house  perched  upon  an 
eminence  at  the  opposite  side  of  the  glacier.     This  is 
the   auberge   of  the   Montanvert,  well   known  to   all 
visitors  to  this  portion  of  the  Alps. 

110.  Here  we  cross  the  glacier.     I  should  have  told 
you  that  its  lower  part,  including  the  broken  portion 
we  have  passed,  is  called  the  Glacier  des  Bois ;  while 
the  place  that  we  are  now  about  to  cross  is  the  be- 
ginning of  the  Mer  de  Glace.     You  feel  that  this  term 
is  not  quite  appropriate,  for  the  glacier  here  is  much 
more  like  a  river  of  ice  than  a  sea.     The  valley  which 
it  fills  is  about  half  a  mile  wide. 

111.  The  ice  may  be  riven  where  we  enter  upon  it, 
but  with  the  necessary  care  there  is  no  difficulty  in 
crossing  this  portion  of  the  Mer  de  Glace.     The  clefts 
and  chasms  in  the  ice  are  called  crevasses;  we  shall 
make  their  acquaintance  on  a  grander  scale  by  and  by. 

112.  Look  up  and  down  this  side  of  the  glacier.     It 
is  considerably  riven,  but  as  we  ad  ranee  the  crevasses 


THE  FOKMS   OF  \VATEE  IN  CLOUDS,  EIVERS,  ETC.     43 

will  diminish,  and  we  shall  find  very  few  of  them  at 
the  other  side.  Note  this  for  future  use.  The  ice  is  at 
first  dirty ;  but  the  dirt  soon  disappears,  and  you  come 
upon  the  clean  crisp  surface  of  the  glacier.  You  have 
already  noticed  that  the  clean  ice  is  white,  and  that 
from  a  distance  it  resembles  snow  rather  than  ice.  This 
is  caused  by  the  breaking  up  of  the  surface  by  the 
solar  heat.  When  you  pound  transparent  rock-salt 
into  powder  it  is  as  white  as  table- salt,  and  it  is  the 
minute  fissuring  of  the  surface  of  the  glacier  by  the 
sun's  rays  that  causes  it  to  appear  white.  Within  the 
glacier  the  ice  is  transparent.  After  an  exhilarating 
passage  we  get  upon  the  opposite  lateral  moraine,  and 
ascend  the  steep  slope  from  it  to  the  Montanvert  Inn. 

§  13.   The  Her  de  Glace  and  its  Sources.     Our  First 
Climb  to  the  Cleft  Station. 

113.  Here  the  view  before  us  is  very  grand.  We 
look  across  the  glacier  at  the  beautiful  pyramid  of  the 
Aiguille  du  Dru  (shown  in  our  frontispiece) ;  and  to  the 
right  at  the  Aiguille  des  Charmoz,  with  its  sharp  pin- 
nacles bent  as  if  they  were  ductile.  Looking  straight 
up  the  glacier  the  view  is  bounded  by  the  great  crests 
called  La  Grande  Jorasse,  nearly  14,000  feet  high. 
Our  object  now  is  to  get  into  the  very  heart  of  the 
mountains,  and  to  pursue  to  its  origin  the  wonderful 
frozen  river  which  we  have  just  crossed. 


44  THE  FOKMS  OF  WATER  IN 

114.  Starting  from  the  Montanvert  with  the  glacier 
below  us  to  our  left,  we  soon  reach  some  rocks  resem- 
bling the  Mauvais  Pas ;  they  are  called  Us  Fonts.  We 
cross  them  and  reach  I* Angle,  where  we  quit  the  land  for 
the  ice.  We  walk  up  the  glacier,  but  before  reaching 
the  promontory  called  Trelaporte,  we  take  once  more  to 
the  mountain  side  ;  for  though  the  path  here  has  been 
forsaken  on  account  of  its  danger,  for  the  sake  of  know- 
ledge we  are  prepared  to  incur  danger  to  a  reasonable 
extent.  A  little  glacier  reposes  on  the  slope  to  our 
right.  We  may  see  a  huge  boulder  or  two  poised  on 
the  end  of  the  glacier,  and,  if-  fortunate,  also  see  the 
boulder  liberated  and  plunging  violently  down  the  slope. 
Presence  of  mind  is  all  that  is  necessary  to  render  our 
safety  certain ;  but  travellers  do  not  always  show  pre- 
sence of  mind,  and  hence  the  path  which  formerly  led 
over  this  slope  has  been  forsaken.  The  whole  slope  is 
cumbered  by  masses  of  rock  which  this  little  glacier  has 
sent  down.  These  I  wished  you  to  see ;  by  and  by 
they  shall  be  fully  accounted  for. 

115;  Above  Trelaporte  to  the  right  you  see  a  most 
singular  cleft  in  the  rocks,  in  the  middle  of  which 
stands  an  isolated  pillar,  hewn  out  by  the  weather. 
Our  next  object  is  to  get  to  the  tower  of  rock  to.  the  left 
of  that  cleft,  for  from  that  position  we  shall  gain  a 
most  commanding  and  instructive  view  of  the  Mer  de 
Glace  and  its  sources. 

116.  The  cleft  referred  to,  with  its  pillar,  may  be 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.  45 

seen  to  the  right  of  the  preceding  engraving  of  the  Her 
de  Glace.  Below  the  cleft  is  also  seen  the  little  glacier 
just  referred  to. 

117.  We  may  reach  this  cleft  by  a  steep  gully,  visible 
from  our   present   position,    and   leading   directly   up 
to  the  cleft.     But  these  gullies,  or  couloirs,  are  very 
dangerous,  being  the  pathways  of  stones  falling  from 
the  heights.     We  will  therefore  take  the  rocks  to  the 
left  of  the  gully,  by  close  inspection  ascertain  their  as- 
sailable points,  and  there  attack  them.     In  the  Alps 
as  elsewhere  wonderful  things  may  be  done  by  looking 
steadfastly  at  difficulties,  and  testing  them  wherever 
they  appear  assailable.     We  thus   reach  our  station, 
where  the  glory  of  the  prospect,  and  the  insight  that 
we  gain  as  to  the  formation  of  the  Mer  de  Glace,  far 
more  than  repay  us  for  the  labour  of  our  ascent. 

118.  For  we  see  the  glacier  below  us,  stretching  its 
frozen  tongue  downwards  past  the  Montanvert.     And 
we  now  find  this  single  glacier  branching  out  into  three 
others,  some  of  them  wider  than  itself.     Regard  the 
branch  to  the  right,  the  Glacier  du  Geant.     It  stretches 
smoothly  up  for  a  long  distance,  then  becomes  disturbed, 
and  then  changes  to  a  great  frozen  cascade,  down  which 
the  ice  appears  to  tumble  in  wild  confusion.     Above 
the  cascade  you  see  an  expanse  of  shining  snow,  oc- 
cupying an  area  of  some  square  miles. 


46  THE  FOKMS  OF  WATEK  IN 


§  14.  Ice-cascade  and  Snows  of  the  Col  du  Geant. 

119.  Instead  of  climbing  to  the  height  where  we  now 
stand,  we  might  have  continued  our  walk  upon  the  Mer 
de  Glace,  turned  round  the  promontory  of  Trelaporte, 
and  walked  right  up  the  Glacier  du  Geant.    We  should 
have  found  ice  under  our  feet  up  to  the  bottom  of  the 
cascade.     It  is  not  so  compact  as  the  ice  lower  down, 
but  you  would  not  think  of  refusing  to  call  it  ice. 

120.  As  we  approach  the  fall,  the  smooth  and  un- 
broken character  of  the  glacier  changes  more  and  more. 
We  encounter  transverse  ridges  succeeding  each  other 
with   augmenting   steepness.     The  ice  becomes    more 
and  more  fissured  and   confused.     We  wind  through 
tortuous   ravines,  climb  huge   ice-mounds,  and   creep 
cautiously  along  crumbling  crests,  with  crevasses  right 
and  left.     The  confusion  increases  until  further  advance 
along  the  centre  of  the  glacier  is  impossible. 

121.  But  with  the  aid  of  an  axe  to  cut  steps  in  the 
steeper  ice-walls  and  slopes  we  might,  by  swerving  to 
either  side  of  the  glacier,  work  our  way  to  the  top  of 
the  cascade.     If  we  ascended  to  the  right,  we  should 
have  to  take  care  of  the  ice  avalanches  which  sometimes 
thunder  down  the  slopes ;  if  to  the  left,  we  should  have 
to  take  care  of  the  stones  let  loose  from  the  Aiguille 
Noire.     After  we  had  cleared  the  cascade,  we  should 
have  to  beware  for  a  time  of  the  crevasses,  which  for 


CLOUDS  AND  RIVERS,   ICE   AND   GLACIERS.  47 

some  distance  above  the  fall  yawn  terribly.  But  by 
caution  we  could  get  round  them,  and  sometimes  cross 
them  by  bridges  of  snow.  Here  the  skill  and  know- 
ledge to  be  acquired  only  by  long  practice  come  into 
play ;  and  here  also  the  use  of  the  Alpine  rope  sug- 
gests itself.  For  not  only  are  the  snow  bridges  often 
frail,  but  whole  crevasses  are  sometimes  covered,  the 
unhappy  traveller  being  first  made  aware  of  their  exist- 
ence by  the  snow  breaking  under  his  feet.  Many  lives 
have  thus  been  lost,  and  some  quite  recently. 

122.  Once   upon  the  plateau  above  the   ice-fall  we 
find  the  surface  totally  changed.      Below  the  fall  we 
walked  upon  ice ;    here  we  are  upon  snow.     After  a 
gentle  but  long  ascent  we  reach  a  depression  of  the 
ridge  which  bounds  the  snow-field  at  the  top,  and  now 
look  over  Italy.     We  stand  upon  the  famous  Col  du 
Geant. 

123.  They  were  no  idle  scamperers  on  the  mountains 
that  made  these  wild  recesses  first  known ;  it  was  not 
the  desire  for  health  which  now  brings  some,  or  the 
desire  for  grandeur  and  beauty  which  brings  others,  or 
the  wish  to  be  able  to  say  that  they  have  climbed  a 
mountain  or  crossed  a  col,  which  I  fear  brings  a  good 
many  more  ;  it  was  a  desire  for  knowledge  that  brought 
the  first  explorers  here,  and  on  this  col  the  celebrated 
De  Saussure  lived  for  seventeen  days,  making  scientific 
observations. 


48  THE  FOKMS  OF  WATER  IN 

§  15.  Questioning  the  Glaciers. 

124.  I  would  now  ask  you  to  consider  for  a  moment 
the  facts  which  such  an  excursion  places  in  our  posses- 
sion.    The  snow  through  which  we  have  in  idea  trudged 
is  the  snow  of  last  winter  and  spring.     Had  we  placed 
last   August   a  proper  mark   upon   the  surface  of  the 
snow,  we  should  find  it  this  August  at  a  certain  depth 
beneath   the  surface.     A  good  deal  has  been   melted 
by  the  summer  sun,  but  a  good  deal  of  it  remains,  and 
it  will  continue  until  the  snows  of  the  coming  winter 
fall  and  cover  it.     This  again  will  be  in  part  preserved 
till  next  August,  a  good  deal  of  it  remaining  until  it  is 
covered  by  the  snow  of  the  subsequent  winter.   We  thus 
arrive  at   the  certain   conclusion  that  on  the  plateau 
of  the  Col  du  Geant   the  quantity  of  snow    that  falls 
annually  exceeds  the  quantity  melted. 

125.  Had  we  come  in  the  month  of  April  or  May,  we 
should  have  found  the  glacier  below  the  ice-fall  also 
covered  with  snow,  which  is  now  entirely  cleared  away 
by  the  heat  of  summer.     Nay,  more,  the  ice  there  is 
obviously  melting,  forming  running  brooks  which  cut 
channels  in  the  ice,  and  expand  here  and  there  into 
small   blue-green   lakes.      Hence    you   conclude  with 
certainty  that  below  the  ice-fall  the  quantity  of  frozen 
material  falling  upon  the  glacier  is  less  than  the  quantity 
melted. 

126.  And  this  forces  upon  us  another  conclusion: 


CLOUDS  AND  EIVEES,  ICE  AND   GLACIERS.  49 

between  the  glacier  below  the  ice-fall  and  the  plateau 
above  it  there  must  exist  a  line  where  the  quantity  of 
snow  which  falls  is  exactly  equal  to  the  quantity  annually 
melted.  This  is  the  snow-line.  On  some  glaciers  it  is 
quite  distinct,  and  it  would  be  distinct  here  were  the 
ice  less  broken  and  confused  than  it  actually  is. 

127.  The  French  term  neve  is  applied  to  the  glacial 
region  above  the  snow-line,  while  the  word  glacier  is 
restricted  to  the  ice  below  it.     Thus  the  snows  of  the 
Col  du   Geant  constitute  the  neve  of  the  Glacier  du 
Geant,  and  in  part,  the  neve  of  the  Mer  de  Glace. 

128.  But  if  every  year  thus  leaves  a  residue  of  snow 
upon  the  plateau  of  the  Col  du  Geant,  it  necessarily  fol- 
lows that  the  plateau  must  get  annually  higher,  pro- 
vided  the  snow  remain  upon  it.     Equally  certain  is  the 
conclusion  that  the  whole  length  of  the  glacier  below 
the  cascade  must  sink  gradually  lower,  if  the  waste  of 
annual  melting  le  not  made  good.     Supposing  two  feet  of 
snow  a  year  to  remain  upon  the  Col,  this  would  raise 
it  to  a  height  far  surpassing  that   of  Mont  Blanc  in 
five  thousand  years.    Such  accumulation  must  take  place 
if  the  snow  remain  upon  the  Col ;  but  the  accumulation 
does  not  take  place,  hence  the  snow  does  not  remain 
on  the  Col.    The  question  then  isa  whither  does  it  go  ? 


50 


THE  FORMS   OF  WATER  IN 


SKETCH-PLAN,  SHOWING  THE  MORAINES  &,  b,  C,  d,  6,    OF  THE  MEB  DE  GIJVCE, 


CLOUDS  AND  RIVERS;  ICE  AND  GLACIEKS.  51 

§  16.  Branches  and  Medial  Moraines  of  the  Mer  de  Glace 
from  the  Cleft  Station. 

129.  We  shall  grapple  with  this  question  immediately. 
Meanwhile  look  at  that  ice-valley  in  front  of  us,  stretch- 
ing up  between  Mont  Tacul  and  the  Aiguille  de  Lechaud, 
to  the  base  of  the  great  ridge  called  the  Grande  Jorasse. 
This  is  called  the  Glacier  de  Lechaud.     It  receives  at 
its  head  the  snows  of  the  Jorasse  and  of  Mont  Mallet, 
and  joins  the  Glacier  du  Geant  at  the  promontory  of 
the  Tacul.     The  glaciers  seem  welded  together  where 
they  join,  but  they  continue  distinct.     Between  them 
you  clearly  trace  a  stripe  of  debris  (c  on  the  annexed 
sketch-plan) ;  you  trace  a  similar  though  smaller  stripe 
(a  on  the  sketch),  from   the  junction  of  the   Glacier 
du  Geant  with  the  Glacier  des  Periades  at  the  foot  of 
the  Aiguille  Noire,  which  you  also  follow  along  the  Mer 
de  Glace. 

130.  We  also  see  another  glacier,  or  a  portion  of  it, 
to  the   left,   falling   apparently   in   broken   fragments 
through  a  narrow  gorge  (Cascade  du  Talefre  on  tiie 
sketch)  and  joining  the  Lechaud,  and  from  their  point 
of  junction  also  a  stripe  of  debris  (d)  runs  downwards 
along  the  Mer  de  Glace.     Beyond  this  again  we  notice 
another  stripe  (e),  which  seems  to  begin  at  the  bottom 
of  the  ice-fall,  rising  as  it  were  from  the  body  of  the 
glacier.     Beyond  all  of  these  we  can  notice  the  lateral 
moraine  of  the  Mer  de  Glace. 


52  THE  FOKMS  OF  WATER  IN 

131.  These  stripes  are  the  medial  moraines   of  the 
Mer  de  Glace.     We  shall  learn  more  about  them  im- 
mediately. 

132.  And  now,  having  informed  our  minds  by  these 
observations,  let  our  eyes  wander  over  the  whole  glo- 
rious scene,  the  splintered  peaks  and  the  hacked  and 
jagged  crests,  the  far-stretching  snow-fields,  the  smaller 
glaciers   which  nestle  on  the  heights,  the  deep  blue 
heaven  and  the  sailing  clouds.     Is  it  not  worth  some 
labour  to  gain  command  of  such  a  scene  ?     But  the 
delight  it  imparts  is  heightened  by  the  fact  that  we 
did  not  come  expressly  to  see  it ;  we  came  to  instruct 
ourselves  about  the  glacier,  and  this  high  enjoyment  is 
an  incident  of  our  labour.      You   will   find   it   thus 
through  life ;  without  honest  labour  there  can  be  no 
deep  joy. 

§  17.  The  Tale/re  and  the  Jardin.     Work  among  the 


133.  And  now  let  us  descend  to  the  Mer  de  Glace, 
frr  I  want  to  take  you  across  the  glacier  to  that  broken 
ice-fall  the  origin  of  which  we  have  not  yet  seen.  We 
aim  at  the  farther  side  of  the  glacier,  and  to  reach  it 
we  must  cross  those  dark  stripes  of  debris  which  we 
observed  from  the  heights.  Looked  at  from  above,  these 
moraines  seemed  flat,  but  now  we  find  them  to  be 
ridges  of  stones  and  rubbish,  from  twenty  to  thirty  feet 
high. 


CLOUDS  AND  RIVERS,  ICE  AND   GLACIERS.  53 

134.  We  quit  the  ice  at  a  place  called  the  Couvercle, 
and   wind  round  this  promontory,   ascending   all  the 
time.     We  squeeze  ourselves  through  the  Egralets,  a 
kind  of  natural  staircase  in  the  rock,  and  soon  afterwards 
obtain  a  full  view  of  the  ice -fall,  the  origin  of  which 
we  wish  to  find.     The  ice  upon  the  fall  is  much  broken ; 
we  have  pinnacles  and  towers,  some  erect,  some  lean- 
ing, and  some,  if  we  are  fortunate,  falling  like  those 
upon  the  Glacier  des  Bois ;  and  we  have  chasms  from 
which  issues  a  delicate  blue  light.     With  the  ice-fall  to 
our  right  we  continue  to  ascend,  until  at  length  we 
command  a  view  of  a  huge  glacier  basin,  almost  level, 
and  on  the  middle  of  which  stands  a  solitary  island, 
entirely  surrounded  by  ice.     We  stand  at  the  edge  of 
the  Glacier  du  Talefre,  and  connect  it  with  the  ice-fall 
we  have  passed.     The   glacier  is  bounded  by  rocky 
ridges,  hacked  and  torn  at  the  top  into  teeth  and  edges, 
and  buttressed  by  snow  fluted  by  the  descending  stones. 

135.  We  cross  the  basin  to  the  central  island,  and 
find  grass  and  flowers  at  the  place  where  we  enter  upon 
it.     This  is  the  celebrated  Jardin,  of  which  you  have 
often  heard.     The  upper  part  of  the  Jardin  is  bare  rock. 
Close  at  hand  is  one  of  the  noblest  peaks  in  this  portion 
of  the  Alps,  the  Aiguille  Verte.     It  is  between  thirteen 
and  fourteen  thousand  feet  high,  and  down  its  sides, 
after  freshly-fallen  snow,  avalanches  incessantly  thunder. 
From  one  of  its  projections  a  streak  of  moraine  starts 
down  the  Talefre  ;  from  the  Jardin  also  a  similar  streak 


54  THE  FORMS  OF  WATER  IN 

of  moraine  issues.  Both  continue  side  by  side  to  the 
top  of  the  ice-fall,  where  they  are  engulphed  in  the 
chasms.  But  at  the  bottom  of  the  fall  they  rea-ppear, 
as  if  newly  emerging  from  the  body  of  the  glacier,  and 
afterwards  they  continue  along  the  Mer  de  Glace. 

136.  Walk  with  me  now  alongside  the  moraine  from 
the  Jardin  down  towards  the  ice-fall.     For  a  time  our 
work  is  easy,  such  fissures  as  appear  offering  no  impe- 
diment to   our    march.      But    the   crevasses   become 
gradually  wider  and  wilder,  following    each  other  at 
length  so  rapidly  as  to  leave  merely  walls  of  ice  between 
them.     Here  perfect  steadiness  of  foot  is  necessary — a 
slip  would  be  death.     We  look  towards  the  fall,  and 
observe  the  confusion  of  walls  and  blocks  and  chasms 
below  us  increasing.     At  length  prudence  and  reason 
cry  (  Halt ! '     We  may  swerve  to  the  right  or  to  the 
left,   and  making   our  way  along   crests   of  ice,  with 
chasms  on  both  hands,  reach  either  the  right  lateral 
moraine  or  the  left  lateral  moraine  of  the  glacier. 

§  18.  First  Questions  regarding  Glacier  Motion.     Drift- 
ing of  Bodies  buried  in  a  Crevasse. 

137.  But  what  are  these  lateral  moraines  ?     As  you 
and   I  go  from  day  to   day  along   the   glaciers,  their 
origin  is    gradually  made  plain.  (jW"e  see  at  intervals 
the  stones  and  rubbish  descending  from  the  mountain 
sides  and  arrested  by  the  ice.     All  along  the  fringe  of 
the   glacier   the   stones   and  rubbish  fall,  and  it  soon 


CLOU16  AND  RIVERS,   ICE  AND  GLACIERS.  55 

becomes  evident  that  we  have  here  the  source  of  the 
lateral  moraines."! 

138.  But  how  are  the   medial   moraines  to   be  ac- 
counted for  ?     How  does  the  debris  range  itself  upon  the 
glacier  in  stripes  some  hundreds  of  yards  from  its  edge, 
leaving  the  space  between  them  and  the  edge  clear  of 
rubbish  ?     Some  have  supposed  the  stones  to  have  rolled 
over  the  glacier  from  the  sides,  but  the  supposition  will 
not  bear  examination.     Call  to  mind  now  our  reasoning 
regarding  the   excess   of  snow  which  falls  above  the 
snow-line,  and   our   subsequent   question,  How  is  the 
snow  disposed  of.     Can  it  be  that  the  entire  mass  is 
moving  slowly  downwards  ?     If  so,  the  lateral  moraines 
would  be  carried  along  by  the  ice  on  which  they  rest, 
and  when  two   branch   glaciers   unite  they  would  lay 
their  adjacent  lateral  moraines  together  to  form  a  medial 
moraine  upon  the  trunk  glacier. 

139.  There  is,  in  fact,  no  way  that  we  can  see  of  dis- 
posing of  the  excess  of  snow  above  the  snow-line ;  there 
is  no  way  of  making  good  the  constant  waste  of  the 
ice  below  the  snow-line  ;  there  is  no  way  of  accounting 
for  the  medial  moraines  of  the  glacier,  but  by  supposing 
that  from  the  highest  snow-fields  of  the  Col  du  Geant, 
the  Lechaud,  and  the  Talefre,  to  the  extreme  end  of  the 
Glacier  des  Bois,  the  whole  mass  of  frozen  matter  is 
moving  downwards. 

140.  If  you  were  older,  it  would  give  me  pleasure  to 
take  you  up  Mont  Blanc.     Starting  from  Chamouni,  we 


56  THE  FOEMS  OF  WATER  IN 

should  first  pass  through  woods  and  pastures,  then  up 
the  steep  hill-face  with  the  Glacier  des  Bossons  to  our 
right,  to  a  rock  known  as  the  Pierre  Pointue ;  thence 
to  a  higher  rock  called  the  Pierre  VEclielle,  because  here 
a  ladder  is  usually  placed  to  assist  in  crossing  the 
chasms  of  the  glacier.  At  the  Pierre  1'Echelle  we 
should  strike  the  ice,  and  passing  under  the  Aiguille  du 
Midi,  which  towers  to  the  left,  and  which  sometimes 
sweeps  a  portion  of  the  track  with  stone  avalanches,  we 
should  cross  the  Glacier  des  Bossons  ;  amid  heaped-up 
mounds  and  broken  towers  of  ice  ;  up  steep  slopes  ;  over 
chasms  so  deep  that  their  bottoms  are  hi4  in  darkness. 
141.  We  reach  the  rocks  of  the  Grands  Mulets,  which 
form  a  kind  of  barren  islet  in  the  icy  sea;  thence 
to  the  higher  snow-fields,  crossing  the  Petit  Plateau, 
which  we  should  find  cumbered  by  blocks  of  ice. 
Looking  to  the  right,  we  should  see  whence  they  came, 
for  rising  here  with  threatening  aspect  high  above  us 
are  the  broken  ice-crags  *  of  the  Dome  du  Goute.  The 
guides  wish  to  pass  this  place  in  silence,  and  it  is  just 
as  well  to  humour  them,  however  much  you  may  doubt 
the  competence  of  the  human  voice  to  bring  the  ice- 
crags  down.  Prom  the  Petit  Plateau  a  steep  snow- slope 
would  carry  us  to  the  Grand  Plateau,  and  at  day-dawn 
1  know  nothing  in  the  whole  Alps  more  grand  and 
solemn  than  this  place. 

*  Named  seracs  from  their  resemblance  in  shape  and  colour  to  an  inferior 
kind  of  curdy  cheese  called  by  this  name  at  Chamouni. 


CLOUDS  AND  EIVERS,  ICE  AND   GLACIERS. 


57 


142.  One  object  of  our  ascent  would  be  now  attained ; 
for  here  at  the  head  of  the  Grand  Plateau,  and  at  the 
foot  of  the  final  slope  of  Mont  Blanc,  I  should  show  you 
a  great  crevasse,  into  which  three  guides  were  poured 
by  an  avalanche  in  the  year  1820. 

143.  Is   this   language  correct?     A  crevasse  hardly 


CREVASSE  ON  GRAND  PLATEAU. 


to  be  distinguished  from  the  present  one  undoubtedly 
existed  here  in  1820.  But  was  it  the  identical  crevasse 
now  existing  ?  Is  the  ice  riven  here  to-day  the  same 
as  that  riven  fifty-one  years  ago  ?  By  no  means.  How 
is  this  proved  ?  By  the  fact  that  more  than  forty  years 
after  their  interment,  the  remains  of  those  three  guides 


58  THE  FOEMS  OF  WATER  IN 

were  found  near  the  end  of  the  Glacier  des  Bossons,  many 
miles  below  the  existing  crevasse. 

144.  The  same  observation  proves  to  demonstration 
that  it  is  the  ice  near  the  bottom  of  the  higher  neve 
that  becomes  the  surface-ice  of  the  glacier  near  its  end. 
The  waste  of  the  surface  below  the  snow-line  brings 
the  deeper  portions  of  the  ice  more  and  more  to  the 
light  of  day. 

145.  There  are  numerous  obvious  indications  of  the 
existence   of  glacier  motion,  though  it  is  too  slow  to 
catch  the  eye  at  once.     The  crevasses  change  within 
certain  limits  from  year  to  year,  and  sometimes  from 
month  to  month ;  and  this  could  not  be  if  the  ice  did 
not  move.     Bocks  and  stones  also  are  observed,  which 
have  been  plainly  torn  from  the  mountain  sides.     Blocks 
seen  to   fall    from    particular    points   are   afterwards 
observed    lower    down.  (On   the    moraines   rocks   are 
found  of  a  totally  different  mineralogical  character  from 
those  composing  the  mountains  right  and  left ;  and  in 
all  such  cases  strata  of  the  same  character  are  found 
bordering  the  glacier  higher  up.     Hence  the  conclusion 
that  the  foreign  boulders  have  been  floated  down  by 
the  ice.     Further,  the  ends  or '  snouts '  of  many  glaciers 
act  like  ploughshares  on  the  land  in  front  of  them, 
overturning  with  slow  .but  merciless  energy  huts  and 
chalets   that   stand   in   their   way.     Facts   like   these 
have  been  long  known  to  the  inhabitants  of  the  High 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.  59 

Alps,  who  were  thus  made  acquainted  in  a  vague  and 
general  way  with  the  motion  of  the  glaciers. 

§  19.   The  Motion  of  Glaciers.     Measurements  ~by  Hugi 
and  Agassis.      Drifting  of  Huts  on  the  Ice. 

146.  But  the  growth  of  knowledge  is  from  vagueness 
towards  precision,  and  exact  determinations  of  the  rate 
of  glacier   motion    were   soon   desired.      With   refer- 
ence to  such  measurements  one  glacier  in  the  Bernese 
Oberland  will  remain  for  ever  memorable.     From  the 
little  town  of  Meyringen  in   Switzerland  you  proceed 
up  the  valley  of  Hasli,  past  the  celebrated  waterfall  of 
Handeck,  where  the  river  Aar  plunges  into  a  chasm 
more  than  200  feet  deep.     You  approach  the  Grimsel 
Pass,  but  instead  of  crossing  it  you  turn  to  the  right  and 
follow  the  course  of  the  Aar  upwards.     Like  the  Rhone 
and  the  Arveiron,  you  find  the  Aar  issuing  from  a  glacier. 

147.  Get  upon  the   ice,  or  rather  upon  the   deep 
moraine  shingle  which  covers  the  ice,  and  walk  upwards. 
It  is  hard  walking,  but  after  some  time  you  get  clear 
of  the  rubbish,  and  on  to  a  wide   glacier  with  a  great 
medial  moraine  running  along  its  back.     This  moraine 
is  formed  by  the  junction  of  two  branch  glaciers,  the 
Lauteraar  and  the  Finsteraar,  which  unite  at  a  pro- 
montory  called  the   Abschwung    to   form  the   trunk 
glacier  of  the  Unteraar. 

148.  On  this  great  medial  moraine  in  1827  an  intrepid 


60  THE  FOKMS  OF  WATER  IN 

and  enthusiastic  Swiss  professor,  Hugi,  of  Solothurm 
(French  Soleure),  built  a  hut  with  a  view  to  observa- 
tions upon  the  glacier.  His  hut  moved,  and  he 
measured  its  motion.  In  the  three  years — from  1827 
to  1830 — it  had  moved  330  feet  downwards.  In  1836 
it  had  moved  2,354  feet ;  and  in  1841  M.  Agassiz  found 
it  4,712  feet  below  its  first  position. 

149.  In  1840,  M.  Agassiz  himself  and   some   bold 
companions  took  shelter  under   a   great   overhanging 
slab  of  rock  on  the  same  moraine,  to  which  they  added 
side  walls  and  other  means  of  protection.     And  because 
he  and  his  comrades  came  from  Neufchatel,  the  hut 
was  called  long  afterwards  the  '  Hotel  des  Neuchatelois.' 
Two  years  subsequent  to  its  erection  M.  Agassiz  found 
that  the  'hotel '  had  moved  486  feet  downwards. 

§  20.  Precise  Measurements  of  Agassiz  and  Forbes. 
Motion  of  a  Glacier  proved  to  resemble  the  Motion 
of  a  River. 

150.  We  now  approach  an  epoch  in  the  scientific 
history   of    glaciers.      Had    the   first   observers    been 
practically   acquainted   with  the   instruments  of  pre- 
cision used  in  surveying,  accurate  measurements  of  the 
motion   of  glaciers   would  probably  ha,ve  been  earlier 
executed.     We  are  now  on  the  point  of  seeing  such 
instruments  introduced   almost  simultaneously  by  M. 
Agassiz  on  the  glacier  of  the  Unteraar,  and  by  Professor 
Forbes  on  the  Mer  de  Glace.     Attempts  had  been  made 


CLOUDS  AND  EIVERS,  ICE  AND  GLACIERS.  61 

by  M.  E seller  de  la  Linth  to  determine  the  motion  of 
a  series  of  wooden  stakes  driven  into  the  Aletsch 
glacier,  but  the  melting  was  so  rapid  that  the  stakes 
goon  fell.  To  remedy  this,  M.  Agassiz  in  1841  under- 
took the  great  labour  of  carrying  boring  tools  to  his 
6  hotel,'  and  piercing  the  Unteraar  glacier  at  six  different 
places  to  a  depth  of  ten  feet,  in  a  straight  line  across 
the  glacier.  Into  the  holes  six  piles  were  so  firmly 
driven  that  they  remained  in  the  glacier  for  a  year,  and 
in  1842  the  displacements  of  all  six  were  determined. 
They  were  found  to  be  160  feet,  225  feet,  269  feet,  245 
feet,  210  feet,  and  125  feet,  respectively. 

151.  A  great  step  is  here  gained.     You  notice  that 
the  middle  numbers  are  the  largest.     They  correspond 
to  the  central  portion  of  the   glacier.     Hence,  these 
measurements  conclusively  establish,  not  only  the  fact 
of  glacier  motion,  but  that  the  centre  of  the  glacier,  like 
that  of  a  river,  moves  more  rapidly  than  the  sides. 

152.  With  the  aid  of  trained  engineers  M.  Agassiz 
followed  up  these  measurements  in  subsequent  years. 
His  researches  are  recorded  in  a  work  entitled  c  Systeme 
glaciaire,'  which  is  accompanied  by  a  very  noble  Atlas 
of  the  Glacier  of  the  Unteraar,  published  in  1847. 

153.  These  determinations  were  made  by  means  of  a 
theodolite,  of  which  1  will  give  you  some  notion  im- 
mediately.    The  same  instrument  was   employed  the 
same  year  by  the  late  Principal  Forbes  upon  the  Mer  de 
Glace.    He  established  independently  the  greater  central 


62  THE  FORMS  OF  WATER  IN 

motion.  He  showed,  moreover,  that  it  is  not  necessary 
to  wait  a  year,  or  even  a  week  to  determine  the  motion 
of  a  glacier;  with,  a  correctly- adjusted  theodolite  he 
was  able  to  determine  the  motion  of  various  points  of 
the  Mer  de  Glace  from  day  to  day.  He  affirmed,  and 
with  truth,  that  the  motion  of  the  glacier  might  be 
determined  from  hour  to  hour.  We  shall  prove  this 
farther  on  (162).  Professor  Forbes  also  triangulated 
the  Mer  de  Glace,  and  laid  down  an  excellent  map  of 
it.  His  first  observations  and  his  survey  are  recorded 
in  a  celebrated  book  published  in  1843,  and  entitled 
*  Travels  in  the  Alps.5 

154.  These  observations  were  also   followed   up   in 
subsequent  years,  the  results  being  recorded  in  a  series 
of  detached  letters  and  essays  of  great  interest.     These 
were  subsequently  collected  in  a  volume  entitled  ( Occa- 
sional Papers  on  the  Theory  of  Glaciers,'  published  in 
1859.     The  labours  of  Agassiz  and  Forbes  are  the  two 
chief  sources  of  our  knowledge  of  glacier  phenomena. 

§  21.  The  Theodolite  and  its  Use.     Our  own 
Measurements. 

155.  My  object  thus  far  is  attained.     I  have  given 
you  proofs  of  glacier  motion,  and  a  historic  account  of 
its   measurement.     And   now  we   must  try  to   add  a 
little  to  the  knowledge  of  glaciers  by  our  own  labours 
on  the  ice.     Resolution  must  not  be  wanting  at  the 
commencement   of  our   work,   nor   steadfast  patience 


CLOUDS  AND  EIVEES,   ICE  AND   GLACIEES.  63 

during  its  prosecution.  Look  then  at  this  theodolite ; 
it  consists  mainly  of  a  telescope  and  a  graduated  circle, 
the  telescope  capable  of  motion  up  and  down,  and  the 
circle,  carrying  the  telescope  along  with  it,  capable  of 
motion  right  and  left.  When  desired  to  make  the 
motion  exceedingly  fine  and  minute,  suitable  screws, 
called  tangent  screws,  are  employed.  The  instrument 
is  supported  by  three  legs,  movable,  but  firm  when 
properly  planted. 

156.  Two  spirit-levels  are  fixed  at  right  angles  to 
each  other   on  the   circle  just  referred  to.     Practice 
enables  one  to  take  hold  of  the  legs  of  the  instrument, 
and  so  to   fix  them   that   the   circle   shall  be   nearly 
horizontal.     By  means   of    four    levelling    screws   we 
render   it   accurately    horizontal.     Exactly   tinder    the 
centre  of  the  instrument  is  a  small  hook  from  which  a 
plummet   is   suspended ;    the   point   of   the   bob  just 
touches  a  rock  on  which  we  make  a  mark ;  or  if  the 
earth  be   soft   underneath,   we   drive  a  stake  into  it 
exactly  under  the   plummet.     By  re- suspending  the 
plummet  at  any  future  time  we  can  find  to  a  hairbreadth 
the  position  occupied  by  the  instrument  to-day. 

157.  Look  through  the  telescope;  you  see  it  crossed 
by  two  fibres  of  the  finest  spider's  thread.     In  actual 
work  we  first  direct  the  telescope  across  the  glacier, 
until    the    intersection    of  the   two   fibres    accurately 
covers  some  well-defined  point  of  rock  or  tree  at  the  other 
side  of  the  valley.     This,  our  fixed  standard,  we  sketch 


64  THE  FOKMS  OF  WATEK  IN 

with  its  surroundings  in  a  note-book,  so  as  to  be  able 
immediately  to  recognise  it  on  our  return  to  this  place. 
Imagine  a  straight  line  drawn  from  the  centre  of  the 
telescope  to  this  point,  and  that  this  line  is  permitted 
to  drop  straight  down  upon  the  glacier,  every  point  of 
it  falling  as  a  stone  would  fall ;  along  such  a  line  we 
have  now  to  fix  a  series  of  stakes. 

158.  A  trained  assistant  is  already  upon  the  glacier. 
He  erects  his  staff  and  stands  behind  it ;  the  telescope 
is   lowered  without    swerving  to   the   right  or  to   the 
left ;  in  mathematical  language  it  remains  in  the  same 
vertical  plane.      The   crossed   fibres   of    the   telescope 
probably  strike  the  ice  a  little  away  from  the  staff  of 
the  assistant ;  by  a  wave  of  the  arm  he  moves  right  or 
left ;  he  may  move  too  much,  so  we  wave  him  back 
again.     After  a  trial  or  two  he  knows  whether  he  is 
near  the  proper  point,  and  if  so  makes  his  motions 
small.     He  soon  exactly  strikes  the  point  covered  by 
the  intersection  of  the  fibres.     A  signal  is  made  which 
tells  him  that  he  is  right ;  he  pierces  the  ice  with  an 
auger  and  drives  in  a  stake.     He  then  goes  forward,  and 
in  precisely  the  same  manner  takes  up  another  point. 
After   one   or  two   stakes    have   been   driven   in,   the 
assistant   is  able   to   take   up   the   other  points   very 
rapidly.     Any  requisite  number  of  stakes  may  thus  be 
fixed  in  a  straight  line  across  the  glacier. 

159.  Next  morning  we  measure  the  motion  of  all  the 
stakes.     The  theodolite  is  mounted  in  its  former  posi- 


CLOUDS  AND  EIVERS,  ICE  AND  GLACIERS.  65 

tion  and  carefully  levelled.  The  telescope  is  directed 
first  upon  the  standard  point  at  the  opposite  side  of 
the  valley,  being  moved  by  a  tangent  screw  until  the 
intersection  of  the  spider's  threads  accurately  covers 
the  point.  The  telescope  is  then  lowered  to  the 
first  stake,  beside  which  our  trained  assistant  is 
already  standing.  He  is  provided  with  a  staff  with 
feet  and  inches  marked  on  it.  A  glance  shows  us 
that  the  stake  has  moved  down.  By  our  signals  the 
assistant  recovers  the  point  from  which  we  started 
yesterday,  and  then  determines  the  distance  from  this 
point  to  the  stake.  It  is,  say,  6  inches ;  through 
this  distance,  therefore,  the  stake  has  moved. 

160.  We  are  careful  to  note  the  hour  and  minute  at 
which  each  stake  is  driven  in,  and  the  hour  and  the 
minute   when   its   distance   from   its    first  position  is 
measured;  this  enables  us  to   calculate   the  accurate 
daily  motion  of  the  point  in  question.     The  distances 
through  which  all  the  other  points   have  moved   are 
determined  in  precisely  the  same  way. 

161.  Thus  we  shall  proceed   to  work,  first   making 
clear  to  our  minds  what  is  to  be  done,  and  then  making 
sure  that  it  shall  be  accurately  done.     To  give  our  work 
reality,   I  will  here  record  the   actual  measurements 
executed,  and  the  actual  thoughts  suggested,  on  the 
Mer   de    Glace   in   1857.     The   only  unreality   that  I 
would  ask  you  to  allow,  is  that  you  and  I  are  supposed 
to  be  making  the  observations  together.     The  labour 


66  THE  FOKMS   OF  WATER  IN 

of  measuring   was   undertaken  for  the  most  part  by 
Mr.  Hirst. 

§  22.  Motion  of  the  Her  de  Glace. 

162.  On  July  14,  then,  we  find  ourselves  at  the  end 
of  the  Glacier  des  Bois,  not  far  from  the  source  of  the 
Arveiron.     We  direct  our  telescope  across  the  glacier, 
and  fix  the  intersection  of  its  spider's  threads   accu- 
rately upon  the  edge  of  a  pinnacle  of  ice.    We  leave  the 
instrument  untouched,  looking  through  it  from   hour 
to  hour.     The  edge  of  ice  moves  slowly,  but  plainly, 
past  the  fibres,  and  at  the  end  of  three  hours  we  assure 
ourselves  that  the   motion   has    amounted   to  several 
inches.   While  standing  near  the  vault  of  the  Arveiron, 
and  talking  about  going  into  it,  its  roof  gives  way,  and 
falls  with  the  sound  of  thunder.     It  is  not,  therefore, 
without  reason  that  I   warned  you  against    entering 
these  vaults  in  summer. 

163.  We  ascend  to  the  Montanvert  Inn,  fix  on  it  as 
a  residence,  and  then  descend  to  the  lateral  moraine  of 
the  glacier  a  little  below  the  inn.     Here  we  erect  our 
theodolite,  and  mark  its  exact  position  by  a  plummet. 
We  must  first  make  sure  that  our  line  is  perpendicular, 
or  nearly  so,  to  the  axis  or  middle  line  of  the  glacier. 
Our  instructed  assistant  lays  down  a  long  staff  in  the 
direction  of  the  axis,  assuring  himself,  by  looking  up  and 
down,  that  it  is  the  true  direction.     With  another  staff 
in  his  hand,  pointed  towards  our  theodolite,  he  shifts 
his  position  until  the  second  staff  is  perpendicular  to  the 


CLOUDS  AND  RIVERS,   ICE  AND  GLACIERS.  67 

first.  Here  lie  gives  us  a  signal.  We  direct  our  tele- 
scope upon  him,  and  then  gradually  raising  its  end  in  a 
vertical  plane  we  find,  and  note  by  sketching,  a  standard 
point  at  the  other  side  of  the  glacier.  This  point  known, 
and  our  plummet  mark  known,  we  can  on  any  future 
day  find  our  line.  (To  render  the  measurements  more 
intelligible,  I  append  on  the  next  page  an  outline  dia- 
gram of  the  Mer  de  Glace,  and  of  its  tributaries.) 

164.  Along  the  line  just  described  ten  stakes  were  set 
on  July  17,  1857.     Their  displacements  were  measured 
on  the   following  day.     Two  of  them  had  fallen,  but 
here   are  the  distances  passed   over  by   the  eight   re- 
maining ones  in  twenty-four  hours. 

DAILY  MOTION  OF  THE  MER  DE  GLACE. 
FIKST  LINE:  A  A'  UPON  THE  SKETCH. 

East  West 

Stake     ...    1       2       3       4       5       7       9      10 
Inches    ...  12     17     23     26     25     26     27     33 

165.  You  have  already   assured  yourself  by   actual 
contact  that  the  body  of  the  glacier  is  real  ice,  and  you 
may   have   read  that   glaciers   move ;    but  the  actual 
observation  of  the  motion  of  a  body  apparently  so  rigid 
is   strangely  interesting.     And  not  only  does   the  ice 
move  bodily,  but  one  part  of  it  moves  past  another; 
the   rate   of    motion   augmenting    gradually   from    12 
inches   a   day   at  the   side   to    33  inches  a  day  at  a 
distance  from  the  side.     This  quicker  movement  of  the 
3entral  ice   of  glaciers  had   been  already  observed  by 


Grande  Jorasse. 


Coldu 

Greaut. 


Chapea 


OUTLINE  PLAN,  SHOWING  THE  MEASURED  LINES  OF  THE  MER  DE  GLACE  AND 
ITS  T1UBUTARIES. 


THE  FORMS  OF  WATER  IN  CLOUDS,  RIVERS,  ETC.     69 

Agassiz  and  Forbes ;  we  verify  their  results,  and  now 
proceed  to  something  new.  Crossing  the  Glacier  du 
Geant,  which  occupies  more  than  half  the  valley,  we 
find  that  our  line  of  stakes  is  not  yet  at  an  end.  The 
10th  stake  stands  on  the  part  of  the  ice  which  conies 
from  the  Talefre. 

166.  Now  the  motion  of  the  sides  is  slow,  because  of 
the  friction  of  the  ice  against  its  boundaries ;  but  then 
one  would  think  that  midway  between  the  boundaries, 
where   the  friction  of  the   sides   is  least,  the  motion 
ought  to  be  greatest.     This  is  clearly  not  the  case ;  for 
though  the  10th   stake  is  nearer  than  the  9th  to  the 
eastern   or  Chapeau  side  of  the  valley,  the   10th  stake 
surpasses  the  9th  by  6  inches  a  day. 

167.  Here  we  have  something  to  think  of;  but  before 
a  natural  philosopher  can  think  with  comfort  he  must 
be  perfectly  sure  of  his  facts.     The  foregoing  line  ran 
across  the  glacier  a  little  below  the  Montanvert.     We 
will  run  another  line  across  a  little  way  above  the  hotel. 
On  July  18  we  set  out  this  line,  and  to  multiply  our 
chances  of  discovery  we  place  along  it  31  stakes.     On 
the  subsequent  day  five  of  these  were  found  unfit  for 
use ;  but   here   are   the   distances   passed  over  by  the 
remaining  six-and-twenty  in  24  hours. 

SECOND  LINE:  BB'  UPON  THE  SKETCH. 
West 

Stake        2   3   4   5   6   7   8   9   10  11  12  13 

Inches       11  12  15  15  16  17  18  19  20  20  21  21 

Stake        15  16  17  18  19  20  21  22  23  24  25  26 

Inches       23  23  23  21  23  21  25  22  22  23  25  26 


70  THE  FORMS  OF  WATER  IN 

168.  Look  at  these  numbers.     The  first  broad  fact 
they  reveal  is  the  advance  in  the  rate  of  motion  from 
first  to  last.     There  are  however  small  irregularities  ; 
from  23  inches  at  the  17th  stake  we  fall  to  21  inches  at 
the  18th ;  from  23  inches  at  the  19th  we  fall  to  21  inches 
at  the  20th;  from  25  inches  at  the  21st  we  fall  to  22 
inches  at  the  22nd  and  23rd  ;  but  notwithstanding  these 
small  ups  and  downs,  the  general  advance  of  the  rate 
of  motion  is  manifest.     Now  there  may  have  been  some 
slight  displacement  of  the  stakes  by  melting,  sufficient 
to  account  for  these  small   deviations  from  uniformity 
in  the  increase  of  the  motion.     But  another  solution  is 
also  possible.     We  shall  afterwards  learn  that  the  gla- 
cier is  retarded  not  only  by  its  sides  but  by  its  bed ; 
that  the  upper  portions  of  the  ice  slide  over  the  lower 
ones.     Now  if  the  bed  of  the  Mer  de  Glace  should  have 
eminences  here  and  there  rising  sufficiently  near  to  the 
surface  to  retard  the  motion  of  the  surface,  they  might 
produce  the  small  irregularities  noticed  above. 

169.  We  note  particularly,  while  upon  the  ice,  that  the 
26th  stake,  like  the  10th  stake  in  our  last  line,  stands 
much  nearer  to  the  eastern  than  to  the  western  side 
of  the  glacier ;  the  measurements,  therefore,  offer  a  fur- 
ther proof  that  the  centre  of  this  portion  of  the  glacier 
is  not  the  place  of  swiftest  motion. 

§  23.  Unequal  Motion  of  the  two  Sides  of  the 
Mer  de  Glace. 

170.  But  in  neither  the  first  line  nor  the  second  were 


CLOUDS  AND  KIVERS,  ICE  AND   GLACIEES.  71 

we  able  to  push  our  measurements  quite  across  the 
glacier.  Why  ?  In  attempting  to  do  one  thing  we  are 
often  taught  another,  and  thus  in  science,  if  we  are  only 
steadfast  in  our  work,  our  very  defeats  are  converted 
into  means  of  instruction.  We  at  first  planted  our 
theodolite  on  the  lateral  moraine  of  the  Mer  de  Glace, 
expecting  to  be  able  to  command  the  glacier  from  side 
to  side.  But  we  are  now  undeceived;  the  centre  of 
the  glacier  proves  to  be  higher  than  its  sides,  and  from 
our  last  two  positions  the  view  of  the  ice  near  the  oppo- 
site side  of  the  glacier  was  intercepted  by  the  eleva- 
tion at  the  centre.  The  mountain  slopes,  in  fact,  are 
warm  in  summer,  and  they  melt  the  ice  nearest  to  them, 
thus  causing  a  fall  from  the  centre  to  the  sides. 

171.  But  yonder  on  the  heights  at  the  other  side  of 
the  glacier  we  see  a  likely  place  for  our  theodolite. 
We  cross  the  glacier  and  plant  our  instrument  in  a 
position  from  which  we  sweep  the  glacier  from  side  to 
side.  Our  first  line  was  below  the  Montanvert,  our 
second  line  above  it ;  this  third  line  is  exactly  opposite 
the  Montanvert ;  in  fact,  the  mark  on  which  we  have 
fixed  the  fibre-cross  of  the  theodolite  is  a  corner  of  one 
of  the  windows  of  the  little  inn.  Along  this  line  we 
fix  twelve  stakes  on  July  20.  On  the  21st  one  of  them 
had  fallen ;  but  the  velocities  of  the  remaining  eleven 
in  24  hours  were  found  to  be  as  follows : — 


72  THE  FOEMS   OF  WATER  IN 

THIRD  LINE  :  C  C'  UPON  THE  SKETCH. 
East  West 

Stake  ..123456789  10     11 

Inches      .  20     23     29     30     34     28     25     25     25  18      9 

172.  Both  the  first  stake  and  the  eleventh  in  this 
series   stood  near  the  sides  of  the  glacier.      On  the 
eastern   side   the   motion  is    20  inches,  while  on  the 
western  side  it  is  only  9.     It  rises  on  the  eastern  side 
from  20  to  34  inches  at  the  5th  stake,  which  we,  stand- 
ing upon  the  glacier,  can  see  to  be  much  nearer  to  the 
eastern  than  to  the  western  side.     The  united  evidence 
of  these  three   lines  places  the  fact   beyond  doubt,   that 
opposite  the  Montanvert,  and  for  some  distance  above  it 
and  below  it,  the  whole  eastern  side  of  the  glacier  is  moving 
more  quickly  than  the  western  side. 

§  24.  Suggestion  of  a  new  Likeness  of  Glacier  Motion 
to  River  Motion.     Conjecture  tested. 

173.  Here  we  have  cause  for  reflection,  and  facts  are 
comparatively  worthless  if  they  do  not  provoke   this 
exercise  of  the  mind.     It  is  because  facts  of  nature  are 
not  isolated  but  connected,  that  science,  to  follow  them, 
must  also  form  a  connected  whole.     The  mind  of  the 
natural  philosopher  must,  as  it  were,  be  a  web  of  thought 
corresponding  in  all  its  fibres  with  the  web  of  fact  in 
nature. 

174.  Let  us,  then,  ascend  to  a  point  which  commands 
a  good  view  of  this  portion  of  the  Mer  de  Glace.     The 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.  73 

ice-river  we  see  is  not  straight  but  curved,  and  its  cur- 
vature is  from  the  Montanvert ;  that  is  to  say,  its  con- 
vex side  is  east,  and  its  concave  side  is  west  (look  to 
the  sketch).  You  have  already  pondered  the  fact  tha,t 
a  glacier,  in  some  respects,  moves  like  a  river.  How  would 
a  river  move  through  a  curved  channel  ?  This  is  known. 
Were  the  ice  of  the  Mer  de  Glace  displaced  by  water, 
the  point  of  swiftest  motion  at  the  Montanvert  would 
not  be  the  centre,  but  a  point  east  of  the  centre,  Can 
it  be  then  that  this  '  water-rock,'  as  ice  is  sometimes 
called,  acts  in  this  respect  also  like  water? 

175.  This  is  a  thought  suggested  on  the  spot;  it  may 
or  it  may  not  be  true,  but  the  means  of  testing  it  are  at 
hand.     Looking  up  the  glacier,  we  see  that  at  les  Pouts 
it  also  bends,  but  that  there  its  convex  curvature  is 
towards  the  western  side  of  the  valley  (look  again  to 
the   sketch).      If  our  surmise   be  true,  the   point   of 
swiftest  motion  opposite  les  Pouts  ought  to  lie  west  of 
the  axis  of  the  glacier. 

176.  Let  us  test  this  conjecture.     On  July  25  we  fix 
in  a  line  across  this  portion  of  the  glacier  seventeen 
stakes ;  every  one  of  them  has  remained  firm,  and  on 
the   26th  we  find  the  motion  for   24  hours  to  be  as 
follows :  - 

FOUBTH  LINE:  DD'  UPON  THE  SKETCH. 

East  West 

Stake    .123       4       5       6       7  8       9      10     11     32  13     14     15 

Inches  .  7     8     13     15     16     19     20  21     21     23    23     21  22     17     15 


74  THE  FORMS  OF  WATER  IN 

177.  Inspected  by  the  naked  eye  alone,  the  stakes  10 
and  11,  where  the  glacier  reaches  its  greatest  motion, 
are  seen  to  be  considerably  to  the  west  of  the  axis  of 
the  glacier.     Thus  far  we  have  a  perfect  verification  of 
the  guess  which  prompted  us  to  make  these  measure- 
ments.    You  will  here  observe  that  the  c  guesses '  of 
science  are  not  the  work  of  chance,  but  of  thoughtful 
pondering  over  antecedent  facts.     The  guess  is  the  c  in- 
duction' from  the  facts,  to  be  ratified  or  exploded  by  the 
test  of  subsequent  experiment. 

178.  And   though   even  now   we   have  exceedingly 
strong  reason  for  holding  that  the  point  of  maximum, 
velocity  obeys  the  law  of  liquid  motion,  the  strength  of 
our  conclusion  will  be  doubled  if  we  can  show  that  the 
point  shifts  back   to  the  eastern  side  of  the  axis    at 
another  place  of  flexure.      Fortunately  such  a   place 
exists  opposite  Trelaporte.     Here  the  convex  curvature 
of  the  valley  turns  again  to  the  east.     Across  this  por- 
tion of  the  glacier  a  line  was  set  out  on  July  28,  and 
from  measurements  on  the  31st,  the  rate  of  motion  per 
24  hours  was  determined. 

FIFTH  LINE:  EE'  UPON  THE  SKKTCH. 

West  East 

Stake    .1      2      3      4      5      6      7       8       9  10     11  12     13     14     15 

Inches.  11     14    13    15    15    16    17     19     20  19     20  18     16     15     10 

179.  Here,  again,  the  mere  estimate  of  distances  by 
the  eye  would  show  us  that  the  three  stakes  which  moved 
fastest,  viz.  the  9th,  10th,  and  llth,  were  all  to  the  east  of 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.  75 

the  middle  line  of  the  glacier.  The  demonstration  that 
the  point  of  swiftest  motion  wanders  to  and  fro  across 
the  axis,  as  the  flexure  of  the  valley  changes,  is,  there- 
fore,— shall  I  say  complete  ? 

180.  Not  yet.     For  if  surer  means  are  open  to  us  we 
must  not  rest  content  with  estimates  by  the  eye.     We 
have  with  us  a  surveying  chain  :  let  us  shake  it  out  and 
measure  these  lines,  noting  the  distance  of  every  stake 
from  the  side  of  the  glacier.     This  is  no  easy  work 
among  the  crevasses,  but  I  confide  it  confidently  to  Mr. 
Hirst  and  you.     We  can  afterwards  compare  a  number 
of  stakes  on  the  eastern  side  with  the  same  number  of 
stakes  taken  at  the  same  distances  from  the  western 
side.     For  example,  a  pair  of  stakes,  one  ten  yards  from 
the  eastern  side  and  the  other  ten  yards   from  the 
western  side ;  another  pair,  one  fifty  yards  from  the 
eastern  side  and  the  other  fifty  yards  from  the  western 
side,  and  so  on,  can  be  compared  together.     For  the 
sake  of  easy  reference,  let  us  call  the  points  thus  com- 
pared in  pairs,  equivalent  points. 

181.  There  were  five  pairs  of  such  points  upon  our 
fourth  line,  D  D',  and  here  are  their  velocities  : — 

Eastern  points ;  motion  in  inches    .     .  13         15         16         18         20 
Western  points        „  „         .     .  15         17         22         23         23 

In  every  case  here  the  stake  at  the  western  side  moved 
more  rapidly  than  the  equivalent  stake  at  the  eastern 
side. 

182.  Applying  the  same  analysis  to  our  fifth  line, 


76  THE  FOEMS  OF  WATER  IN 

E  E',  we  have  the  following  series  of  velocities  of  three 
pairs  of  equivalent  points  : — 

Eastern  points ;  motion  in  inches    .     .  15         18         19 
Western  points        „  „         .     .  13         15         17 

183.  Here  the  three  points  on  the  eastern  side  move 
more  rapidly  than  the  equivalent  points  on  the  western 
side. 

184.  It  is  thus  proved : — 

1.  That  opposite  the  Montanvert  the  eastern  half  of  the 
Mer  de  Glace  moves  more  rapidly  than  the  western  half. 

2.  That  opposite  les  Fonts    the   western   half  of  the 
glacier  moves  more  rapidly  than  the  eastern  half. 

3.  That    opposite    Trelaporte  the  eastern  half   of  the 
glacier  again  moves  more  rapidly  than  the  western  half. 

4.  That  these  changes  in  the  place  of  greatest  motion 
are  determined  by  the  flexures  of  the  valley  through  which 
the  Mer  de  Glace  moves. 

§25.  New  Law  of  Glacier  Motion. 

185.  Let  us  express  these  facts  in  another  way.  Sup- 
posing the  points  of  swiftest  motion  for  a  very  great 
number  of  lines  crossing  the  Mer  de  Glace  to  be  deter- 
mined ;  the  line  joining  all  those  points   together   is 
what  mathematicians  would  call  the  locus  of  the  point 
of  swiftest  motion. 

186.  At  Trelaporte  this  line  would  lie  east  of  the 
centre ;  at  the  Fonts  it  would  lie  west  of  the  centre ; 
hence  in  passing  from  Trelaporte  to  the  Fonts  it  would 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.  77 

tf 

cross  the  centre.  But  at  the  Montanvert  it  would  again 
lie  east  of  the  centre ;  hence  between  the  Fonts  and  the 
Montanvert  the  centre  must  be  crossed  a  second  time. 
If  there  were  further  sinuosities  upon  the  Mer  de  Glace 
there  would  be  further  crossings  of  the  axis  of  the  glacier. 

187.  The  points  on  the  axis  which  mark  the  transition 
from  eastern  to  western  bending,  and  the  reverse,  may 
be  called  points  of  contrary  flexure. 

188.  Now  what  is  true  of  the  Mer  de  Glace  is  true  of 
all  other  glaciers  moving  through  sinuous  valleys ;  so 
that  the  facts  established  in  the  Mer  de  Glace  may  be 
expanded  into  the  following  general  law  of  glacier  mo- 
tion : — 

When  a  glacier  moves  through  a  sinuous  valley,  the  locus 
of  the  point  of  maximum  motion  does  not  coincide  with 
the  centre  of  the  glacier,  but,  on  the  contrary,  always 
lies  on  the  convex  side  of  the  central  line.  The  locus  is 
therefore  a  curved  line  more  deeply  sinuous  than  the  valley 
itself,  and  crosses  the  axis  of  the  glacier  at  each  point  of 
contrary  flexure. 

189.  The  dotted  line  on  the  Outline  Plan  (page  68) 
represents  the  locus  of  the  point  of  maximum  motion, 
the  firm  line  marking  the  centre  of  the  glacier. 

190.  Substituting  the  word  river  for  glacier,  this  law 
is  also  true.     The  motion  of  the  water  is  ruled  by  pre- 
cisely the  same  conditions  as  the  motion  of  the  ice. 

191.  Let  us  now  apply  our  law  to  the  explanation 
of  a  difficulty.     Turning  to  the  careful  measurements 


78  THE  FORMS   OF  WATER  IN 

executed  by  M.  Agassiz  on  the  glacier  of  the  Unteraar, 
we  notice  in  the  discussion  of  these  measurements  a 
section  of  the  '  Systeme  glaciaire '  devoted  to  the 
'  Migrations  of  the  Centre.'  It  is  here  shown  that  the 
middle  of  the  Unteraar  glacier  is  not  always  the  point 
of  swiftest  motion.  This  fact  has  hitherto  remained 
without  explanation  ;  but  a  glance  at  the  Fnteraar 
valley,  or  at  the  map  of  the  valley,  shows  the  enigma 
to  be  an  illustration  of  the  law  which  we  have  just 
established  on  the  Mer  de  Glace. 

§  26.  Motion  of  Axis  of  Mer  de  Glace. 

192.  We  have  now  measured  the  rate  of  motion  of 
five  different  lines  across  the  trunk  of  the  Mer  de  Glace. 
Do  they  all  move  alike  ?     No.     Like  a  river,  a  glacier 
a,t  different  places  moves  at  different  rates.     Comparing 
together  the  points  of  maximum  motion  of  all  five  lines, 
we  have  this  result : — 

MOTION  OF  MER  DE  GLACE. 

At  Tr&aporte     .         .  .  .20  inches  a  day. 

Mies  Fonts         .         .  .  .     23      „  „ 

Above  the  Montanvert  .  .     26      ,,  „ 

At  the  Montanvert      .  .  .     34      „  „ 

Below  the  Montanvert  .  .     33*    „  ,, 

193.  There  is  thus  an  increase  of  rapidity  as  we  de- 
scend the  glacier  from  Trelaporte  to  the  Montanvert ; 

*  This  is  probably  under  the  mark.  I  think  it  likely  that  the  swiftest 
motion  of  this  portion  of  the  Mer  de  Glace  in  1857  amounted  to  a  yard  in 
twenty-four  hours. 


CLOUDS  AND  RIVERS,  ICE  AND   GLACIERS.  79 

the  maximum  motion  at  the  Montanvert  being  fourteen 
inches  a  day  greater  than  at  Trelaporte. 

§  27.  Motion  of  Tributary  Glaciers. 

194.  So  much  for  the  trunk  glacier;   let    us   now 
investigate  the  branches,  permitting,  as  we  have  hitherto 
done,  reflection  on  known  facts  to  precede  our  attempts 
to  discover  unknown  ones. 

195.  As  we  stood  upon  our  'cleft  station,'  whence 
we  had  so  capital  a  view  of  the  Mer  de  Glace,  we  were 
struck  by  the  fact  that  some  of  the  tributaries  of  the 
glacier  were  wider  than  the  glacier  itself.     Supposing 
water  to  be  substituted  for  the  ice,  how  do  you  suppose 
it  would  behave  ?     You  would  doubtless  conclude  that 
the  motion  down  the  broad  and  slightly-inclined  valleys 
of  the  Geant  and  the  Lechaud  would  be  comparatively 
slow,  but  that  the  water  would  force  itself  with  increased 
rapidity  through  the  'narrows'  of  Trelaporte.     Let  us 
test  this  notion  as  applied  to  the  ice. 

196.  Planting  our  theodolite  in  the  shadow  of  Mont 
Tacul,  and  choosing  a  suitable  point  at  the  opposite  side 
of  the  Glacier  du  Geant,  we  fix  on  July  29  a  series  of 
ten  stakes  across  the  glacier.     The  motion  of  this  line 
in  twenty-four  hours  was  as  follows  : — 

MOTION  OF  GLACIER  DU  GEANT. 

SIXTH  LINE:  HH'  TTPON  SKETCH. 

Stake     ..123456789     10 
Inches  .     .  11     10     12     13     12     13     11     10     9      6 


80  THE  FORMS  OF  WATER  IN 

197.  Our  conjecture  is  fully  verified.     The  maximum 
motion  here  is  seven  inches  a  day  less  than  that  of  the 
Mer  de  Glace  at  Trelaporte  (192). 

198.  And  now  for  the  Lechaud  branch.     On  August 
1  we  fix  ten  stakes  across  this  glacier  above  the  point 
where  it  is  joined  by  the  Talefre.     Measured  on  August 
3,  and  reduced  to  twenty-four  hours,  the  motion  was 
found  to  be — 

MOTION  OF  GLACIER  DE  LECHAUD. 

SEVENTH  LINE:  KK'  UPON  SKETCH. 
Stake  ..12      3      456789     10 
Inches  '.58     10     998697      6 

199.  Here  our  conjecture  is  still  further  verified,  the 
rate  of  motion  being  even  less  than  that  of  the  Glacier 
du  Geant. 

§  28.  Motion  of  Top  and  Bottom  of  Glacier. 

200.  We  have  here  the  most  ample  and  varied  evi- 
dence that  the  sides  of  a  glacier,  like  those  of  a  river, 
are  retarded  by  friction  against  its  boundaries.     But 
the  likeness  does  not  end  here.     The  motion  of  a  river 
is  retarded  by  the    friction   against    its    bed.      Two 
observers,  viz.  Prof.  Forbes  and  M.  Charles  Martins, 
concur  in  showing  the   same  to  be   the   case  with  a 
glacier.     The  observations  of  both  have  been  objected 
to ;  hence  it  is  all  the  more  incumbent  on  us  to  seek 
for  decisive  evidence. 

201.  At  the  Tacul  (near  the  point  a  upon  the  sketch 


CLOUDS  AND  BIVERS,  ICE  AND  GLACISES.  81 

plan,  p.  83)  a  wall  of  ice  about  150  feet  high,  has  already 
attracted  our  attention.  Bending  round  to  join  the 
Lechaud  the  Glacier  du  Geant  is  here  drawn  away  from 
the  mountain  side,  and  exposes  a  fine  section.  We  try 
to  measure  it  top,  bottom,  and  middle,  and  are  defeated 
twice  over.  We  try  it  a  third  time  and  succeed.  A 
stake  is  fixed  at  the  summit  of  the  ice-precipice,  another 
at  4  feet  from  the  bottom,  and  a  third  at  35  feet  above 
the  bottom.  These  lower  stakes  are  fixed  at  some  risk 
of  boulders  falling  upon  us  from  above ;  but  by  skill 
and  caution  we  succeed  in  measuring  the  motions  of  all 
three.  For  24  hours  the  motions  are  : — 

Top  stake        .         ...     6  inches. 
Middle  stake   .         .         .        .     4|     „ 
Eottom  stake   .        .         .         .    2f    „ 

202.  The  retarding  influence  of  the  bed  of  the  glacier 
is  reduced  to  demonstration   by  these   measurements. 
The  bottom  does  not  move  with  half  the  velocity  of  the 
surface. 

§  29.  Lateral  Compression  of  a  Glacier. 

203.  Furnished  with    the   knowledge   which  these 
labours  and  measurements  have  given  us,  let  us  once 
more  climb  to  our  station  beside  the  Cleft  under  the 
Aiguille  de  Charmoz.      At  our  first  visit  we  saw  the 
medial  moraines  of  the  glacier,  but  we  knew  nothing 
about  their  cause.     We  now  know  that  they  mark  upon 
the  trunk  its  tributary  glaciers.     Cast  your  eye,  then, 


82  THE  FORMS  OF  WATER  IN 

first  upon  the  Glacier  du  Geaiit;  realise  its  width  in 
its  own  valley,  and  see  how  much  it  is  narrowed  at 
Trelaporte.  The  broad  ice-stream  of  the  Lechaud  is 
still  more  surprising,  being  squeezed  upon  the  Mer  de 
Glace  to  a  narrow  white  band  between  its  bounding 
moraines.  The  Talefre  undergoes  similar  compression. 
Let  us  now  descend,  shake  out  our  chain,  measure, 
and  express  in  numbers  the  width  of  the  tributaries, 
and  the  actual  amount  of  compression  suffered  at  Tre- 
laporte. 

204.  We  find  the  width  of  the  Glacier  du  Geant  to 
be  5,155  links,  or  1,134  yards. 

205.  The  width  of  the  Glacier  de  Lechaud  we  find 
to  be  3,725  links,  or  825  yards. 

206.  The  width  of  the  Talefre  we  find  to  be  2,900 
links,  or  638  yards. 

207.  The   sum  of  the  widths  of  the   three   branch 
glaciers  is  therefore  2,597  yards. 

208.  At  Trelaporte  these  three  branches  are  forced 
through  a  gorge  893  yards  wide,  or  one-third  of  their 
previous  width,  at  the  rate  of  twenty  inches  a  day. 

209.  If  we  limit  our  view  to  the  Glacier  de  Lechaud, 
the  facts  are  still  more  astonishing.     Previous  to  its 
junction  with  the  Talefre,  this  glacier  has  a  width  of 
825  yards ;  in  passing  through  the  jaws  of  the  granite 
vice  at  Trelaporte,  its  width  is  reduced  to  eighty-eight 
yards,  or  in  round  numbers  to  one-tenth  of  its  previous 
width.     (Look  to  the  sketch  on  the  next  page.) 


CLOUDS  AND  EIVEES,  ICE  AND  GLACIEKS.  83 


SKETCH-PLAX  SHOWING  THE  MORAINES  a,  b,  C,  d,  6,  OF  THE  MER  DE  GLAOE. 


84  THE  FOEMS  OF  WATER  IN 

210.  Are  we  to  understand  by   this  that  the  ice  of 
the   Lechaud   is  squeezed  to  one-tenth  of  its  former 
volume  ?     By  no  means.     It  is  mainly  a  change  of  form, 
not  of  volume,  that  occurs  at  Trelaporte.     Previous  to 
its   compression,  the  glacier   resembles   a  plate  of  ice 
lying  flat    upon   its   bed.      After    its    compression,  it 
resembles  a  plate  fixed  upon  its  edge.     The  squeezing, 
doubtless,  has  deepened  the  ice. 

§  30.  Longitudinal  Compression  of  a  Glacier. 

211.  The  ice  is  forced  through  the  gorge  at  Trela- 
porte by  a  pressure  from  behind;  in  fact  the  Glacier 
du  Geant,  immediately  above  Trelaporte,  represents  a 
piston   or   a  plug   which  drives    the  ice  through  the 
gorge.     What  effect  must  this  pressure  have  upon  the 
plug  itself?     Reasoning  alone  renders  it  probable  that 
the  pressure  will  shorten  the  plug  ;  that  the  lower  part 
of  the  Glacier  du  Geant  will  to  some  extent  yield  to  the 
pressure  from  behind. 

212.  Let  us  test  this  notion.     About  three-quarters 
of  a  mile  above  the  Tacul,  and  on  the  mountain  slope  to 
the  left  as  we  ascend,  we  observe  a  patch  of  verdure. 
Thither  we  climb ;  there  we  plant  our  theodolite,  and 
set  out  across  the  Glacier  du  Geant,  a  line,  which  we 
will  call  line  No.  1  (F  F  upon  sketch,  p.  68). 

213.  About  a  quarter  of  a  mile  lower  down  we  find  a 
practicable  couloir  on  the  mountain  side;   we  ascend 


CLOUDS  AND  RIVERS,  ICE  AND   GLACIERS.  85 

it,  reach  a  suitable  platform,  plant  our  instrument,  and 
set  out  a  second  line,  No.  2  (G  G'  upon  sketch).  We 
must  hasten  our  work  here,  for  along  this  couloir  stones 
are  discharged  from  a  small  glacier  which  rests  upon 
the  slope  of  Mont  Tacul. 

214.  Still  lower  down  by  another  quarter  of  a  mile, 
which  brings  us  near  the  Tacul,  we  set  out  a  third  line, 
No.  3  (H  H'  upon  sketch),  across  the  glacier. 

215.  The  daily  motion  of  the  centres  of  these  three 
lines  is  as  follows  : — 


Inches 

Distances  asunder 

No.  1   . 

.     20-551 

.     545  yards. 

No.  2   . 

.     15-43  1   ' 

No.  3   . 

.     12-75  /   * 

.     487      „ 

216.  The  first  line  here  moves  five  inches  a  day  more 
than  the  second  ;  and  the  second  nearly  three  inches  a 
day  more  than  the  third.     The  reasoning  is  therefore 
confirmed.     The  ice-plug,  which  is  in  round  numbers 
one  thousand  yards  long,  is  shortened  by  the  pressure 
exerted  on  its  front  at  the  rate  of  about  eight  inches  a 
day. 

217.  A  river  descending  the  Yalley  du  Geant  would 
behave  in  substantially  the  same  fashion.   It  would  have 
its  motion  on  approaching  Trelaporte  diminished,  and 
it  would  pour  through  the  defile  with  a  velocity  greater 
than  that  of  the  water  behind. 


86  THE  FOKMS  OF  WATER  IN 

§  31.  Sliding  and  Flowing.     Hard  Ice  and  Soft  Ice. 

218.  We  have  thus   far   confined  ourselves  to  the 
measurement  and  discussion  of  glacier  motion ;  but  in 
our  excursions  we  have  noticed  many  things  besides. 
Here  and  there,  where  the  ice  has  retreated  from  the 
mountain  side,  we  have  seen  the  rocks  fluted,  scored, 
and  polished ;  thus  proving  that  the  ice  had  slidden  over 
them  and  ground  them  down.     At  the  source  of  the 
Arveiron  we  noticed  the  water  rushing  from  beneath 
the   glacier   charged   with    fine   matter.      All   glacier 
rivers    are    similarly  charged.     The  Rhone   carries  its 
load  of  matter  into  the  Lake  of  Geneva ;  the  rush  of 
the  river  is  here  arrested,  the  matter  subsides,  and  the 
Rhone  quits  the  lake  clear  and  blue.     The  Lake  of 
Geneva,  and  many  other  Swiss  lakes,  are  in  part  filled 
up  with  this  matter,  and  will,  in  all  probability,  finally 
be  obliterated  by  it. 

219.  One  portion  of  the  motion  of  a  glacier  is  due  to 
this  bodily  sliding  of  the  mass  over  its  bed. 

220.  We  have  seen  in  our  journeys  over  the  glacier 
streams  formed  by  the  melting  of  the  ice,  and  escaping 
through  cracks  and  crevasses  to  the  bed  of  the  glacier. 
The  fine  matter  ground  down  is  thus  washed  away ; 
the  bed  is  kept  lubricated,  and  the  sliding  of  the  ice 
rendered  more  easy  than  it  would  otherwise  be. 

221.  As  a  skater  also  you  know  how  much  ice  is 
weakened  by  a  thaw.   Before  it  actually  melts  it  becomes 


CLOUDS  AND  EIVERS,  ICE  AND  GLACIEES.  87 

rotten  and  unsafe.  Test  such  ice  with  your  penknife : 
you  can  dig  the  blade  readily  into  it,  or  cut  the  ice  with 
ease.  Try  good  sound  ice  in  the  same  way  :  you  find 
it  much  more  resistant.  The  one,  indeed,  resembles 
soft  chalk ;  the  other  hard  stone. 

222.  Now  the  Mer  de  Glace  in  summer  is   in  this 
thawing  condition.   Its  ice  is  rendered  soft  and  yielding 
by  the   sun;    its  motion   is   thereby   facilitated.     We 
have  seen  that  not  only  does  the  glacier  slide  over  its 
bed,  but  that  the  upper  layers   slide    over  the   under 
ones,  and  that  the  centre  slides  past  the  sides.     The 
softer  and  more  yielding  the  ice  is,  the  more  free  will 
be  this  motion,  and  the  more  readily  also  will  it  be 
forced  through  a  defile  like  Trelaporte. 

223.  But  in  winter  the  thaw  ceases;  the  quantity  of 
water  reaching  the  bed  of  the  glacier  is  diminished  or 
entirely  cut  off.     The  ice  also,  to  a  certain  depth  at 
least,  is  frozen  hard.    These  considerations  would  justify 
the  opinion  that  in  winter  the  glacier,  if  it  moves  at 
all,  must  move  more  slowly  than  in  summer.     At  all 
events,  the  summer  measurements  give  no  clue  to  the 
winter  motion. 

224.  This  point  merits  examination.     I  will  not,  how- 
ever, ask  you  to  visit  the  Alps  in  mid- winter;  but,  if 
you  allow  me,  I  will  be  your  deputy  to  the  mountains, 
and  report  to  you  faithfully  the  aspect  of  the  region 
and  the  behaviour  of  the  ice. 


88  THE  FOKMS  OF  WATER  IN 

§  32.   Winter  on  the  Mer  de  Glace. 

225.  The  winter  chosen  is  an  inclement  one.     There 
is  snow  in  London,  snow  in  Paris,  snow  in  Geneva ; 
snow  near  Chamouni  so  deep  that  the  road  fences  are 
entirely  effaced.     On  Christmas  night — nearly  at  mid- 
night— 1859,  your  deputy  reaches  Chamouni. 

226.  The  snow  fell  heavily  on  December  26  ;  but  on 
the    27th,  during  a  lull  in  the  storm,  we  turn   out. 
There  are  with  me  four  good  guides  and  a  porter.    They 
tie  planks  to  their  feet  to  prevent  them  from  sinking 
in  the  snow ;  I  neglect  this  precaution  and  sink  often 
to  the  waist.     Four  or  five  times  during  our  ascent 
the  slope  cracks  with  an  explosive  sound,  and  the  snow 
threatens  to  come  down  in  avalanches.* 

The  freshly-fallen  snow  was  in  that  particular  con- 
dition which  causes  its  granules  to  adhere,  and  hence 
every  flake  falling  on  the  trees  had  been  retained  there. 
The  laden  pines  presented  beautiful  and  often  fantastic 
forms. 

227.  After  five  hours  and  a  half  of  arduous  work  the 
Montanvert  was  attained.     We  unlocked  the  forsaken 
auberge,  round  which  the  snow  was  reared  in  buttresses. 
I  have  already  spoken  of  the  complex  play  of  crystallising 

*  Four  years  later,  viz.  in  the  spring  of  1863,  a  mighty  climber  and 
noble  guide  and  companion  of  mine,  named  Johann  Joseph  Bennen,  was 
lost,  through  the  cracking  and  subsequent  slipping  of  snow  on  such  a 
slope. 


CLOUDS  AND  EIVEES,   ICE  AND  GLACIERS. 


89 


forces.  The  frost-figures  on  the  window-panes  of  the 
auberge  were  wonderful:  mimic  shrubs  and  ferns 
wrought  by  the  building  power  while  hampered  bj 
the  adhesion  between  the  glass  and  the  film  in  which  it 
worked.  The  appearance  of  the  glacier  was  very  inapres- 


SXOW-LADEN  PINK-TREE.  . 


sive ;  all  sounds  were  stilled.  The  cascades  which  in 
summer  fill  the  air  with  their  music  were  silent,  hanging 
from  the  ledges  of  the  rocks  in  fluted  columns  of  ice. 
The  surface  of  the  glacier  was  obviously  higher  than  it 
had  "been  in  summer;  suggesting  the  thought  that  while 
the  winter  cold  maintained  the  lower  end  of  the  glacier 


90  THE  FORMS  OF  WATER  IN 

jammed  between  its  boundaries,  the  upper  portions  still 
moved  downwards  and  thickened  the  ice.  The  peak  of 
the  Aiguille  du  Dru  shook  out  a  cloud-banner,  the  ori- 
gin and  nature  of  which  have  been  already  explained  (84). 
(See  Frontispiece.) 

228.  On  the  morning  of  the   28th  this  banner  was 
strikingly  large  and  grand,  and  reddened  by  the  light 
of  the  rising  sun,  it  glowed  like  a   flame.      Eoses   of 
cloud   also   clustered  round  the  crests  of  the  Grande 
Jorasse    and  hung   upon   the  pinnacles    of   Charmoz. 
Four  men,  well  roped  together,  descended  to  the  glacier. 
I  had  trained  one  of  them  in  1857,  and  he  was  now  to 
fix  the  stakes.     The  storm  had  so  distributed  the  snow 
as  to  leave  alternate  lengths  of  the  glacier  bare  and 
thickly  covered.     Where  much  snow  lay  great  caution 
was   required,  for  hidden  crevasses  were  underneath. 
The  men  sounded  with  their  staffs  at  every  step.     Once 
while  looking  at  the  party  through  my  telescope  the 
leader  suddenly  disappeared ;  the  roof  of  a  crevasse  had 
given   way  beneath   him ;    but  the   other  three   men 
promptly  gathered  round  and  lifted  him  out   of  the 
fissure.     The  true  line  was  soon  picked  up  by  the  theo- 
dolite ;  one  by  one  the  stakes  were  fixed  until  a  series 
of  eleven  of  them  stood  across  the  glacier. 

229.  To  get  higher  up  the  valley  was  impracticable  ; 
the  snow  was  too  deep,  and  the  aspect  of  the  weather 
too  threatening ;  so  the  theodolite  was  planted  amid  the 
pines  a  little  way  below  the  Montanvert,  whence  through 


CLOUDS  AND   RIVERS,  ICE  AND   GLACIERS.  91 

a  vista  I  could  see  across  the  glacier.  The  men  were 
wrapped  at  intervals  by  whirling  snow-wreaths  which 
quite  hid  them,  and  we  had  to  take  advantage  of  the 
lulls  in  the  wind.  Fitfully  it  came  up  the  valley,  dark- 
ening the  air,  catching  the  snow  upon  the  glacier,  and 
tossing  it  throughout  its  entire  length  into  high  and 
violently  agitated  clouds,  separated  from  each  other  by 
cloudless  spaces  corresponding  to  the  naked  portions  of 
the  ice.  In  the  midst  of  this  turmoil  the  men  con- 
tinued to  work.  Bravely  and  steadfastly  stake  after 
stake  was  set,  until  at  length  a  series  of  ten  of  them 
was  fixed  across  the  glacier. 

230.  Many  of  the  stakes  were  fixed  in  the  snow. 
They  were  four  feet  in  length,  and  were  driven  in  to  a 
depth  of  about  three  feet.  But  that  night,  while  list- 
ening to  the  wild  onset  of  the  storm,  I  thought  it  pos- 
sible that  the  stakes  and  the  snow  which  held  them 
might  be  carried  bodily  away  before  the  morning. 
The  wind,  however,  lulled.  We  rose  with  the  dawn,  but 
the  air  was  thick  with  descending  snow.  It  was  all 
composed  of  those  exquisite  six-petaled  flowers,  or  six- 
rayed  stars,  which  have  been  already  figured  and  de- 
scribed (§  9).  The  weather  brightening,  the  theodo- 
lite was  planted  at  the  end  of  the  first  line.  The  men 
descended,  and,  trained  by  their  previous  experience, 
rapidly  executed  the  measurements.  The  first  line  was 
completed  before  11  A.M.  Again  the  snow  began  to  fall, 
filling  all  the  air.  Spangles  innumerable  were  showered 


92  THE  FORMS   OF  WATER  IN 

upon  the  heights.     Contrary  to  expectation,  the  men 
could  be  seen  and  directed  through  the  shower. 

231.  To  reach  the  position  occupied  by  the  theodolite 
at  the  end  of  our  second  line,  I  had  to  wade  breast-deep 
through  snow  which  seemed  as  dry  and  soft  as  flour. 
The  toil  of  the  men  upon  the  glacier  in  breaking  through 
the  snow  was  prodigious.     But  they  did  not  flinch,  and 
after  a  time  the  leader  stood  behind  the  farthest  stake, 
and  cried,  Nous  avons  fini.     I   was   surprised  to  hear 
him  so  distinctly,  for  falling  snow  had  been  thought 
very  deadening  to  sound.     The  work  was  finished,  and 
I  struck  my  theodolite  with  a  feeling  of  a  general  who 
had  won  a  small  battle. 

232.  We  put  the  house  in  order,  packed  up,  and  shot 
by  glissade  down  the  steep  slopes  of  La  Filia  to  the 
vault  of  the  Arveiron.     We  found  the  river  feeble,  but 
not  dried  up.    Many  weeks  must  have  elapsed  since  any 
water  had  been   sent  down  from  the  surface  of  the 
glacier.     But  at  the  setting  in  of  winter  the  fissures 
were  in  a  great  measure  charged  with  water ;  and  the 
Arveiron  of  to-day  was  probably  due  to  the  gradual 
drainage  of  the  glacier.     There  was  now  no  danger  of 
entering  the  vault,  for  the  ice  seemed  as  firm  as  marble. 
In  the  cavern  we  were   bathed  by   blue  light.     The 
strange  beauty  of  the  place  suggested  magic,  and  put 
me  in  mind  of  stories  about  fairy  caves  which  I  had  read 
when  a  boy.     At  the  source  of  the  Arveiron  our  winter 
visit  to  the   Mer  de  Glace  ends ;  next   morning  your 
deputy  was  on  his  way  to  London. 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.  93 

§  33.   Winter  Motion  of  the  Her  de  Glace. 

233.  Here    are  the  measurements  executed  in  the 

winter  of  1859  :— 

LINE  No.  I. 

Stake  ..12   3   4   5   6   7   8   9   10  11 
Inches  .  .  7  11  14  13  14  14  16  16  12  12  7 

LINE  No.  II. 

Stake    ..123456789      10 
Inches  ..  8     10     14     16     16     16     18     17     15     14 

234.  Thus  the  winter  motion  of  the  Mer  de  Glace 
near  the  Montanvert  is,   in  round  numbers,  half  the 
summer  motion. 

235.  As  in  summer,  the  eastern  side  of  the  glacier  at 
this  place  moved  quicker  than  the  western. 

§  34.  Motion  of  the  Grindelwald  and  Aletsch  Glaciers. 

236.  As  regards  the  question  of  motion,  to  no  other 
glacier  have  we  devoted  ourselves  with  such  thorough- 
ness as  to  the  Mer  de  Glace ;    we  are,  however,  able 
to  add  a  few  measurements  of  other  celebrated  glaciers. 
Near  the  village  of  Grindelwald  in  the  Bernese  Ober- 
land,   there   are   two  great  ice-streams  called  respec- 
tively the  Upper  and  the  Lower  Grindelwald  glaciers, 
the  second  of  which  is  frequently  visited  by  travellers 
in  the  Alps.     Across  it  on  August  6,  1860,  a  series  of 
twelve  stakes  was  fixed  by  Mr.  Yaughan  Hawkins  and 
myself.     Measured  on  the  8th  and  reduced  to  its  daily 
rate,  the  motion  of  these  stakes  was  as  follows  : — 


94  THE  FOEMS  OF  WATER  IN 

MOTION  OF  LOWER  GRINDELWALD  GLACIER. 

East  West 

Stake  ..1       2       3       4       5       6       7       8       9      10     11     12 
Inches      .  18     19     20     21     21     21     22     20     19     18     17     14 

237.  The  theodolite  was  here  planted  a  little  below 
the  footway  leading  to  the  higher  glacier  region,  and  at 
about  a  mile  above  the  end  of  the  glacier.     The  mea- 
surement was  rendered  difficult  by  crevasses. 

238.  The  largest  glacier  in  Switzerland  is  the  Great 
Aletsch,  to  whieh  further  reference  shall  subsequently 
be  made.     Across  it  on  August  14,  1860,  a  series  of 
thirty-four  stakes  was  planted  by  Mr.  Hawkins  and  me. 
Measured  on  the  16th  and  reduced  to  their  daily  rate, 
the  velocities  were  found  to  be  as  follows  : — 

MOTION  OF  GREAT  ALETSCH  GLACIER. 

East 

Stake  ..12345       6       7       8  9      10     11  12 

Inches      .23468      11     13     14  16     17     17  19 

Stake  .     .13     14     15     16     17     18     19  20     21     22  23 

Inches      .  19     18     18     17     19     19     19  19     17     17  15 

Stake  .     .24     25     26     27     28     29     30  31     32     33  34 

Inches      .  16     17     17     17     17     17     17  17     16     12  12 

West 

239.  The  maximum  motion  here  is  nineteen  inches  a 
day.    Probably  the  eastern  side  of  the  glacier  is  shallow, 
the  retardation  of  the  bed  making  the  motion  of  the 
eastern  stakes  inconsiderable.     The  width  of  the  glacier 
here  is  9,030  links,  or  about   a   mile    and   a   furlong. 
The  theodolite  was  planted  high  among  the  rocks  on 
the  western  flank  of  the  mountain,  about  half  a  mile 
above  the  Margelin  See. 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.  95 

§  35.  Motion  of  Morteratsch  Glacier. 

240.  Far  to  the  east  of  the  Oberland  and  in  that 
interesting  part  of  Switzerland  known  as  the  Ober  En- 
gadin,  stands  a  noble  group  of  mountains,  less  in  height 
than  those  of  the   Oberland,  but  still  of  commanding 
elevation.     The  group  derives  its  name  from  its  most 
dominant  peak,  the  Piz  Bernina.     To  reach  the  place 
we  travel  by  railway  from  Basel  to  Zurich,  and  from 
Zurich  to  Chur  (French  Coire),  whence  we  pass  by  dili- 
gence over  either  the  Albula  pass  or  the  Julier  pass  to 
the  village  of  Pontresina.     Here  we  are  in  the  imme- 
diate neighbourhood  of  the  Bernina  mountains. 

241.  From  Pontresina  we  may  walk  or  drive  along  a 
good  coach  road  over  the  Bernina  pass  into  Italy.     At 
about  an  hour  above  the  village  you  would  look  from 
the  road  into  the  heart  of  the  mountains,  the  line  of 
vision  passing  through  a  valley,  in  which  is  couched  a 
glacier  of  considerable  size.     Along  its  back  you  would 
trace  a  medial  moraine,  and  you  could  hardly  fail  to 
notice  how  the  moraine,  from  a  mere   narrow  streak 
at  first,  widens  gradually  as  it  descends,  until  finally  it 
quite  covers  the  lower  end  of  the  glacier.     Nor  is  this 
an  effect  of  perspective ;  for  were  you  to  stand  upon  the 
mountain  slopes  which  nourish  the  glacier,  you  would 
see  thence  also  the  widening  of  the  streak  of  rubbish, 
though  the   perspective   here   would  tend   to   narrow 
the  moraine  as  it  retreats  downwards. 


96  THE  FOBMS   OF  WATEE  IN 

242.  The  ice-stream  here  referred  to  is  the  Morter- 
atsch  glacier,  the  end  of  which  is  a  short  hour's  walk 
from  the  village  of  Pontresina.     We  have  now  to  de- 
termine its  rate  of  motion  and  to  account  for  the  widen- 
ing of  its  medial  moraine. 

243.  In  the  summer  of  1864  Mr.  Hirst  and  myself 
set  out  three  lines  of  stakes  across  the  glacier.     The 
first  line  crossed  the  ice  high  up ;  the  second  a  good 
distance  lower  down,  and  the  third  lower  still.     Even 
the  third  line,  however,  was  at  a  considerable  distance 
above   the   actual   snout   of  the    glacier.      The    daily 
motion  of  these  three  lines  was  as  follows  : — 

FIRST  LINE. 

Stake  ..12   3   4   5   6   7   8   9   10  11 
Inches  ..  8  12  13  13  14  13  12  12  10   7   5 

SECOND  LINE. 

Stake    ..12      3      4      5      6      7      8      910     11 
Inches  ..14       6       8      10     11     11     11     11     11     11 

THIRD  LINE. 

Stake    ..12       3       4       5       6       7       8       9      10     11 
Inches  ..12456677554 

244.  Compare  these  lines  together.     You  notice  the 
velocity  of  the  first  is  greater  than  that  of  the  second, 
and  the  velocity  of  the  second  greater  than  that  of  the 
third. 

245.  The  lines  were  permitted  to  move  downwards  for 


CLOUDS  AND  RIVEES,  ICE  AND  GLACIERS.  97 

100  hours,  at  the  end  of  which  time  the  spaces  passed 
over  by  the  points  of  swiftest  motion  of  the  three  lines 
were  as  follows  : — 

MAXIMUM  MOTION  IN  100  HOTJRS. 

First  line       .        .        .        .56  inches. 
Second  line    .         .         .         .     45      „ 
Third  line      .         .         .         .     30      „ 

246.  Here  then  is  a  demonstration  that  the  upper 
portions  of  the  Morteratsch  glacier  are  advancing  on 
the  lower  ones.     In  1871  the  motion  of  a  point  on  the 
middle  of  the  glacier  near  its  snout  was  found  to  be  less 
than  two  inches  a  day  ! 

247.  What,  then,  is  the  consequence  of  this  swifter 
march  of  the  upper  glacier?     Obviously  to  squeeze  this 
medial  moraine  longitudinally,  and  to  cause  it  to  spread 
out  laterally.  We  have  here  distinctly  revealed  the  cause 
of  the  widening  of  the  medial  moraine. 

248.  It  has  been  a  question  much  discussed,  whether  a 
glacier  is  competent  to  scoop  out  or  deepen  the  valley 
through  which   it   moves,   and   this   very  Morteratsch 
glacier  has  been  cited  to  prove  that  such  is  not  the  case. 
Observers  went  to  the  snout  of  the  glacier,  and  finding 
it  sensibly  quiescent,  they  concluded  that  no  scooping 
occurred.     But  those  who  contended  for  the  power  of 
glaciers  to  excavate  valleys  never  stated,  or  meant  to 
state,  that  it  was  the  snout  of  the  glacier  which  did 
the  work.      In    the  Morteratsch  glacier  the  work  of 
excavation,   which  certainly  goes  on  to  a  greater  or 


98  THE  FORMS  OF  WATER  IN 

less  extent,   must  be  far  more  effectual  high  up  the 
valley  than  at  the  end  of  the  glacier. 

§  36.  Birth  of  a  Crevasse  :  Reflections. 

249.  Preserving  the  notion  that  we  are  working  to- 
gether, we  will  now  enter  upon  a  new  field  of  enquiry. 
We  have  wrapped  up  our  chain,  and  are  turning  home- 
wards after  a  hard  day's  work  upon  the  Glacier  du 
Geant,  when  under  our  feet,  as  if  coming  from   the 
body  of  the  glacier,  an  explosion  is  heard.     Somewhat 
startled,  we  look  enquiringly  over  the  ice.     The  sound 
is  repeated,  several  shots  being  fired  in  quick  succession. 
They  seem  sometimes  to  our  right,  sometimes  to  our 
left,  giving  the  impression  that  the  glacier  is  breaking 
all  round  us.     Still  nothing  is  to  be  seen. 

250.  We  closely  scan  the  ice,  and  after  an  hour's 
strict  search  we  discover  the  cause  of  the  reports.  They 
announce  the  birth  of  a  crevasse.     Through  a  pool  upon 
the  glacier  we  notice  air  bubbles  ascending,  and  find  the 
bottom  of  the  pool  crossed  by  a  narrow  crack,  from 
which  the  bubbles  issue.     Eight  and  left  from  this  pool 
we  trace  the  young  fissure  through  long  distances.     It 
is  sometimes  almost  too  feeble  to  be  seen,  and  at  no 
place  is  it  wide  enough  to  admit  a  knife-blade. 

251.  It  is   difficult   to   believe  that  the   formidable 
fissures  among  which  you  and  I  have  so  often  trodden 
with  awe,  could  commence  in  this  small  way.     Such, 
however,  is  the  case.     The  great  and  gaping  chasms  on 


CLOUDS  AND  RIVERS,   ICE  AND  GLACIERS.  99 

and  above  the  ice-falls  of  the  Geant  and  the  Talefre 
begin  as  narrow  cracks,  which  open  gradually  to 
crevasses.  We  are  thus  taught  in  an  instructive  and 
impressive  way  that  appearances  suggestive  of  very 
violent  action  may  really  be  produced  by  processes  so 
slow  as  to  require  refined  observations  to  detect  them. 
In  the  production  of  natural  phenomena  two  things 
always  come  into  play,  the  intensity  of  the  acting  force, 
and  the  time  during  which  its  acts.  Make  the  in- 
tensity great,  and  the  time  small,  and  you  have  sudden 
convulsion ;  but  precisely  the  same  apparent  effect  may 
be  produced  by  making  the  intensity  small,  and  thfs 
time  great.  This  truth  is  strikingly  illustrated  by  the 
Alpine  ice-falls  and  crevasses;  and  many  geological 
phenomena,  which  at  first  sight  suggest  violent  con- 
vulsion, may  be  really  produced  in  the  selfsame 
almost  imperceptible  way. 

§  37.  Icicles. 

252.  The  crevasses  are  grandest  on  the  higher  neves, 
where  they  sometimes  appear  as  long  yawning  fissures, 
and  sometimes  as  chasms  of  irregular  outline, 
delicate  blue  light  shimmers  from  them,  but  this  is 
gradually  lost  in  the  darkness  of  their  profounder 
portions.  Over  the  edges  of  the  chasms,  and  mostly 
over  the  southern  edges,  hangs  a  coping  of  snow,  and 
from  this  depend  like  stalactites  rows  of  transparent 
icicles,  10,  20,  30  feet  long.  These  pendent  spears 


100  THE  FORMS  OF  WATER  IN 

constitute  one  of  the   most  beautiful  features  of  the 
higher  crevasses. 

253.  How   are   they  produced?     Evidently  by  the 
thawing  of  the  snow.     But  why,  when  once  thawed, 
should  the  water  freeze  again  to  solid   spears?     You 
have   seen  icicles  pendent  from  a  house-eave,  which 
have  been  manifestly  produced  by  the  thawing  of  the 
snow  upon  the  roof.     If  we  understand  these,  we  shall 
also   understand  the   vaster  stalactites  of  the  Alpine 
crevasses. 

254.  Gathering  up  such  knowledge  as  we  possess, 
and  reflecting  upon  it  patiently,  let  us  found  on  it,  if 
we  can,  a  theory  of  icicles. 

255.  First,  then,  you  are  to  know  that  the  air  of  our 
atmosphere  is  hardly  heated  at  all  by  the  rays  of  the 
sun,  whether  visible  or  invisible.     The  air  is   highly 
transparent   to  all  kinds  of  rays,  and  it   is  only  the 
scanty  fraction  to  which  it  is  not  transparent  that  ex- 
pend their  force  in  warming  it. 

256.  Not  so,  however,  with  the  snow  on  which  the 
sunbeams  fall.     It  absorbs  the  solar  heat,  and  on  a 
sunny  day  you  may  see  the  summits  of  the  high  Alps 
glistening  with  .the  water  of  liquefaction.    The  air  above 
and  around  the  mountains  may  at  the  same  time  be 
many  degrees  below  the  freezing  point  in  temperature. 

257.  You  have  only  to  pass  from  sunshine  into  shade 
to  prove  this.     A  single  step  suffices  to  carry  you  from 
a  place  where  the  thermometer   stands  high  to   one 


CLOUDS  AND  K1VERS,  ICE  AND  GLACIEBS.          101 

where  it  stands  low  ;  the  change  being  due,  not  to  any 
difference  in  the  temperature  of  the  air,  but  simply  to 
the  withdrawal  of  the  thermometer  from  the  direct 
action  of  the  solar  rays.  Nay,  without  shifting  the 
thermometer  at  all,  by  interposing  a  suitable  screen, 
which  cuts  off  the  sun's  rays,  the  coldness  of  the  air 
may  be  demonstrated. 

258.  Look  now  to  the  snow  upon  your  house  roof. 
The  sun  plays  upon  it,  and  melts  it ;  the  water  trickles 
to  the  eave  and  then  drops  down.     If  the  eave  face  the 
sun  the  water  remains  water;  but  if  the  eave  do  not 
face  the  sun,  the  drop,  before  its  quits  its  parent  snow, 
is  already  in  shadow.     Now  the  shaded   space,  as   we 
have  learnt,  may  be  below  the  freezing  temperature.    If 
so,   the   drop,    instead   of  falling,   congeals,    and   the 
rudiment   of  an  icicle   is   formed.     Other   drops   and 
driblets  succeed,  which  trickle  over  the  rudiment,  con- 
geal upon  it  in  part  and  thicken  it  at  the  root.     But  a 
portion  of  the  water  reaches  the  free  end  of  the  icicle, 
hangs  from  it,  and  is  there  congealed  before  it  escapes. 
The  icicle  is  thus  lengthened.     In  the  Alps,  where  the 
liquefaction   is  copious   and  the   cold   of  the    shaded 
crevasse  intense,  the  icicles,  though  produced  in  the 
same  way,  naturally  grow  to  a  greater  size.    The  drain- 
age of  the  snow  after  the  sun's  power  is  withdrawn 
also  produces  icicles. 

259.  It  is  interesting  and  important  that  you  should 
be  able  to  explain  the  formation  of  an  icicle ;  but  it  is 


102  THE  FORMS   OF  WATER  IN 

far  more  important  that  you  should  realise  the  way  in 
which  the  various  threads  of  what  we  call  Nature  are 
woven  together.  You  cannot  fully  understand  an  icicle 
without  first  knowing  that  solar  beams  powerful  enough 
to  fuse  the  snows  and  blister  the  human  skin,  nay,  it 
might  be  added,  powerful  enough,  when  concentrated, 
to  burn  up  the  human  body  itself,  may  pass  through 
the  aira  and  still  leave  it  at  an  icy  temperature. 

§  38.   The  Bergschrund. 

260.  Having  cleared  away  this  difficulty,  let  us  turn 
once  more  to  the  crevasses,  taking  them  in  the  order 
of  their  formation.     First  then  above  the  neve  we  have 
the  final  Alpine  peaks  and   crests,  against  which  the 
snow   is    often  reared  as  a  steep  buttress.     We   have 
already  learned  that  both  neves  and  glaciers  are  moving 
slowly  downwards ;  but  it   usually   happens   that  the 
attachment  of  the  highest  portion  of  the  buttress  to  the 
rocks  is  great  enough  to  enable  it  to  hold  on  while 
the  lower  portion  breaks  away.     A  very  characteristic 
crevasse  is  thus  formed,  called  in  the  German-speaking 
portion  of  the  Alps  a  Bergschrund.     It  often  surrounds 
a  peak  like  a  fosse,  as  if  to  defend  it  against  the  as- 
saults of  climbers. 

261.  Look  more  closely  into  its  formation.     Imagine 
the  snow  as  yet  unbroken.     Its  higher  portions  cling 
to  the  rocks,  and  move  downwards  with  extreme  slow- 
ness.    But    its    lower    portions,   whether   from   their 


CLOUDS  AND  EIVERS,  ICE  AND   GLACIERS.          103 

greater  depth,  and  weight,  or  their  less  perfect  attach- 
ment, are  compelled  to  move  more  quickly.  A  pull  is 
therefore  exerted,  tending  to  separate  the  lower  from 
the  upper  snow.  For  a  time  this  pull  is  resisted  by  the 
cohesion  of  the  neve;  but  this  at  length  gives  way, 
and  a  crack  is  formed  exactly  across  the  line  in  which 
the  pull  is  exerted.  In  other  words,  a  crevasse  is  formed 
at  right  angles  to  the  line  of  tension. 

§  39.   Transverse  Crevasses. 

262.  Both  on  the  neve  and  on  the  glacier  the  origin 
of  the  crevasses  is  the  same.     Through  some  cause  or 
other  the  ice  is  thrown  into  a  state  of  strain,  and  as  it 
cannot  stretch  it  breaks  across  the  line  of  tension.     Take, 
for  example,  the  ice-fall  of  the  Geant,  or  of  the  Talefre, 
above   which   you   know  the  crevasses  yawn  terribly. 
Imagine  the  neve  and  the  glacier  entirely  peeled  away, 
so  as  to   expose   the   surface  over  which  they   move. 
From  the  Col  du  Geant  we  should   see  this   surface 
falling  gently  to  the  place  now  occupied  by  the  brow  of 
the  cascade.     Here  the  surface  would  fall  steeply  down 
to  the  bed  of  the  present  Glacier  du  Geant,  where  the 
slope  would  become  gentle  once  more. 

263.  Think  of  the  neve  moving  over  such  a  surface. 
It  descends  from  the  Col  till  it  reaches  the  brow  just 
referred  to.     It  crosses  the  brow,  and  must  bend  down 
to  keep  upon  its  bed.     Realise  clearly  what  must  occur. 
The   surface   of  the  neve   is  evidently  thrown  into  a 

6 


104  THE  FOEMS   OF  WATEK  IN 

state  of  strain  ;  it  breaks  and  forms  a  crevasse.  Each 
fresh  portion  of  the  neve  as  it  passes  the  brow  is 
similarly  broken,  and  thus  a  succession  of  crevasses  is 
sent  down  the  fall.  Between  every  two  chasms  is  a 
great  transverse  ridge.  Through  local  strains  upon  the 
fall  those  ridges  are  also  frequently  broken  across, 
towers  of  ice — seracs — being  the  result.  Down  the  fall 
both  ridges  and  seracs  are  borne,  the  dislocation  being 
augmented  during  the  descent. 

264.  What  must  occur  at  the  foot  of  the  fall?     Here 
the  slope  suddenly  lessens  in  steepness.     It  is  plain  that 
the  crevasses  must  not  only  cease  to  open  here,  but  that 
they  must  in  whole  or  in  part  close  up.     At  the  summit 
of  the  fall,  the  bending  was  such  as  to  make  the  surface 
convex ;  at  the  bottom  of  the  fall  the  bending  renders 
the  surface  concave.     In  the  one  case  we  have  strain,  in 
the  other  pressure.     In  the  one  case,  therefore,  we  have 
the  opening,  and  in  the  other  the  closing  of  crevasses. 
This  reasoning   corresponds  exactly  with  the  facts  of 
observation. 

265.  Lay    bare   your   arm   and   stretch   it  straight. 
Make    two  ink   dots  half  an   inch   or   an   inch  apart, 
exactly  opposite  the  elbow.     Bend  your  arm,  the  dots 
approach  each  other,  and  are  finally  brought  together. 
Let  the  two  dots  represent  the  two  sides  of  a  crevasse 
at  the  bottom  of  an  ice-fall ;  the  bending  of  the  arm 
resembles  the  bending  of  the  ice,  and  the  closing  up  of 
the  dots  resembles  the  closing  of  the  fissures. 


CLOUDS  AND  KIVERS,  ICE  AND  GLACIERS.          105 

266.  The  same  remarks  apply  to  various  portions  of 
the  Mer  de  Glace.     At  certain  places  the  inclination 
changes  from  a  gentler  to  a  steeper  slope,  and  on  cross- 
ing the  brow  between  both  the  glacier  breaks  its  back. 
Transverse  crevasses  are  thus  formed.     There  is  such  a 
change  of  inclination  opposite  to  the  Angle,  and  a  still 
greater  but  similar  change  at  the  head  of  the  Glacier 
des  Bois.     The  consequence  is  that  the  Mer  de  Glace  at 
the  former  point  is  impassable,  and  at  the  latter  the 
rending  and  dislocation  are  such  as  we  have  seen  and 
described.     Below  the  Angle,  and  at  the  bottom  of  the 
Glacier  des  Bois,  the  steepness  relaxes,  the  crevasses 
heal  up,  and  the  glacier  becomes  once  more  continuous 
and  compact. 

§  40.  Marginal  Crevasses. 

267.  Supposing,  then,  that  we  had  no  changes  of 
inclination,  should  we  have  no  crevasses  ?     We  should 
certainly  have  less  of  them,  but  they  would  not  wholly 
disappear.     For  other  circumstances  exist  to  throw  the 
ice  into  a  state  of  strain,  and  to  determine  its  fracture. 
The  principal  of  these  is  the  more  rapid  movement  of 
the  centre  of  the  glacier. 

268.  Helped  by  the  labours  of  an  eminent  man,  now 
dead,  the  late  Mr.  Win.  Hopkins,  of  Cambridge,  let  us 
master  the  explanation  of  this  point  together.     But  the 
pleasure  of  mastering  it  would  be  enhanced  if  we  could 
see  beforehand  the  perplexing  and  delusive  appearances 


106  THE  FOEMS  OF  WATER  IN 

accounted  for  bj  the  explanation.  Could  my  wishes  be 
followed  out,  I  would  at  this  point  of  our  researches  carry 
you  off  with  me  to  Basel,  thence  to  Thun,  thence  to 
Interlaken,  thence  to  Grindelwald,  where  you  would 
find  yourself  in  the  actual  presence  of  the  Wetterhorn 
and  the  Eiger,  with  all  the  greatest  peaks  of  the  Bernese 
Oberland,  the  Finsteraarhorn,  the  Schreckhorn,  the 
Monch,  the  Jungfrau,  at  hand.  At  Grindelwald,  as  we 
have  already  learnt,  there  are  two  well-known  glaciers 
— the  Ober  Grindelwald  and  the  Unter  Grindelwald 
glaciers — on  the  latter  of  which  our  observations  should 
commence. 

269.  Dropping  down  from  the  village  to  the  bottom 
of  the  valley,  we  should  breast  the  opposite  mountain, 
and  with  the  great  limestone  precipices  of  the  Wetter- 
horn  to  our  left,  we  should  get  upon  a  path  which  com- 
mands  a  view  of  the   glacier.     Here   we  should  see 
beautiful  examples  of  the  opening  of  crevasses  at  the 
summit  of  a  brow,  and  their  closing   at   the   bottom. 
But  the  chief  point  of  interest  would  be  the  crevasses 
formed  at  the  side  of  this  glacier — the  marginal  crevasses, 
as  they  may  be  called. 

270.  We  should  find  the  side  copiously  fissured,  even 
at  those  places  where  the  centre  is  compact ;  and  we 
should    particularly    notice    that    the   fissures    would 
neither  run  in  the  direction  of  the  glacier,  nor  straight 
across  it,  but  that  they  would  be  oblique  to  it,  enclosing 
an  angle  of  about  45  degrees  with  the  sides.     Starting 


CLOUDS  AND  KIVEES,   ICE  AND   GLACIERS.        107 


from  the  side  of  the  glacier  the  crevasses  would  be  seen 
to  point  upwards  ;  that  is  to  say,  the  ends  of  the  fissures 
abutting  against  the  bounding  mountain  would  appear 
to  be  dragged  down.  Were  you  less  instructed  than 
you  now  are,  I  might  lay  a  wager  that  the  aspect  of 
these  fissures  would  cause  you  to  conclude  that  the 
centre  of  the  glacier  is  left  behind  by  the  quicker  motion 
of  the  sides. 

271.  This  indeed  was  the  conclusion  drawn  by  M. 
Agassiz   from   this  very   appearance,    before    he   had 
measured   the  motion  of  the  sides  and  centre  of  the 
glacier  of  the  Unteraar.     Intimately  versed  with  the 
treatment  of  mechanical  problems,  Mr.  Hopkins  imme- 
diately deduced  the  obliquity  of  the  lateral  crevasses 
from  the  quicker  flow  of  the  centre.     Standing  beside 
the    glacier   with    pencil    and  note-book    in   hand,    I 
would  at  once  make  the  matter  clear  to  you  thus. 

272.  Let  A  c,  in  the  annexed  figure,  be  one  side  of 
the  glacier,  and  B  D  the  other ;  and  let  the  direction  of 

ASS'  C 


T' 


motion  be  that  indicated  by  the  arrow.     Let  s  T  be  a 
transverse  slice  of  the  glacier,  taken  straight  across  it, 


108  THE  FORMS  OF  WATER  IN 

say  to-day.  A  few  days  or  weeks  hence  this  slice  will 
have  been  carried  down,  and  because  the  centre  moves 
more  quickly  than  the  sides  it  will  not  remain  straight, 
but  will  bend  into  the  form  s'  T'. 

273.  Supposing   T  i  to  be   a   small   square   of  the 
original  slice  near  the  side  of  the  glacier.     In  its  new 
position   the  square  will  be  distorted  to  the  lozenge- 
shaped  figure  T'  i'.    Fix  your  attention  upon  the  diagonal 
T  i  of  the  square  ;  in  the  lower  position  this  diagonal, 
if  the  ice  could  stretch,  would  be  lengthened  to  T'  i'. 
But  the  ice  does  not  stretch ;  it  breaks,  and  we  have 
a  crevasse  formed  at  right  angles  to  T'  i'.     The  mere 
inspection   of  the  diagram  will  assure   you   that   the 
crevasse  will  point  obliquely  upwards. 

274.  Along  the  whole  side  of  the  glacier  the  quicker 
movement  of  the  centre  produces   a  similar  state  of 
strain;    and   the   consequence    is  that  the    sides    are 
copiously  cut  by  those  oblique  crevasses,  even  at  places 
where  the  centre  is  free  from  them. 

275.  It  is  curious  to  see  at  other  places  the  transverse 
fissures  of  the  centre  uniting  with  those  at  the  sides, 
so   as   to   form   great  curved  crevasses  which  stretch 
across  the  glacier  from  side  to  side.     The  convexity  of 
the  curve  is  turned  upwards,  as  mechanical  principles 
declare  it  ought  to  be.     (See  sketch  on  opposite  page.) 
But  if  you  were  ignorant  of  those  principles,  you  would 
never  infer  from  the  aspect  of  these  curves  the  quicker 
motion  of  the  centre.     In  landslips,  and  in  the  motion 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS. 


109 


of  partially  indurated  mud,  you  may  sometimes  notice 
appearances  similar  to  those  exhibited  by  the  ice. 


SKETCH  OF  CURVED  CREV ASSES  :    T1IE  GLACIER  MOVES  FROM  LEFT  TO  1UI!UT. 


§  41.  Longitudinal  Crevasses. 

276.  We  have  thus  unravelled  the  origin  of  both 
transverse  and  marginal  crevasses.  But  where  a  glacier 
issues  from  a  steep  and  narrow  defile  upon  a  com- 
paratively level  plain  which  allows  it  room  to  expand 
laterally,  its  motion  is  in  part  arrested,  and  the  level 
portion  has  to  bear  the  thrust  of  the  steeper  portions 
behind.  Here  the  line  of  thrust  is  in  the  direction  of 
the  glacier,  while  the  direction  at  right  angles  to  this 


110  THE  FORMS   OF  WATEE  IN 

is  one  of  tension.     Across  this  latter  the  glacier  breaks, 
and  longitudinal  crevasses  are  formed. 

277.  Examples  of  this  kind  of  crevasse  are  furnished 
by  the  lower  part  of  the  Glacier  of  the  Rhone,  when 
looked  down  upon  from  the  Grimsel  Pass,  or  from  any 
commanding  point  on  the  flanking  mountains. 

§  42.  Crevasses  in  relation  to  Curvature  of  Glacier. 

278.  One  point  in  addition  remains  to  be  discussed, 
and  your  present  knowledge  will  enable  you  to  master 
it  in  a  moment.     You  remember  at  an  early  period  of 
our  researches  that  we  crossed  the  Mer  de  Glace  from 
the   Chapeau   side   to    the   Montanvert   side.     I  then 
desired  you  to  notice   that  the  Chapeau  side  of  the 
glacier  was  more  fissured  than  either  the  centre  or  the 
Montanvert  side  (75).     Why  should  this  be  so  ?     Know- 
ing as  we  now  do  that  the  Chapeau  side  of  the  glacier 
moves  more  quickly  than  the  other ;  that  the  point  of 
maximum  motion  does  not  lie  on  the  centre  but  far  east 
of  it,  we  are  prepared  to  answer  this  question  in  a  per- 
fectly satisfactory  manner. 

279.  Let  A  B  and  c  D,  in  the  diagram  opposite,  re- 
present the  two  curved  sides  of  the  Mer  de  Glace  at  the 
Montanvert,  and  let  m  n  be  a  straight  line  across  the 
glacier.     Let  o  be  the  point  of  maximum  motion.     The 
mechanical  state  of  the  two  sides  of  the  glacier  may 
be  thus  made  plain.     Supposing  the  line  m  n  to  be  a 
straight  elastic  string  with  its  ends  fixed ;  let  it  be 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS. 


Ill 


grasped  firmly  at  the  point  o  by  the  finger  and  thumb, 
and  drawn  to  o',  keeping  the  distance  between  of  and 


Montanvert 


the  side  c  D  constant.  Here  the  length,  n  o  of  the  string 
would  have  stretched  to  n  o',  and  the  length  m  o  to  m  o', 
and  you  see  plainly  that  the  stretching  of  the  short  line, 
in  comparison  with  its  length,  is  greater  than  that  of 
the  long  line  in  comparison  with  its  length.  In  other 
words,  the  strain  upon  n  o'  is  greater  than  that  upon 
mo';  so  that  if  one  of  them  were  to  break  under  the 
strain,  it  would  be  the  short  one. 

280.  These  two  lines  represent  the  conditions  of  strain 
upon  the  two  sides  of  the  glacier.     The  sides  are  held 
back,  and  the  centre  tries  to  move  on,  a  strain  being 
thus   set  up  between  the  centre   and  sides.     But  the 
displacement  of  the  point  of  maximum  motion  through 
the  curvature  of  the  valley  makes  the  strain  upon  the 
eastern  ice  greater  than  that  upon  the  western.     The 
eastern  side  of  the  glacier  is  therefore  more  crevassed 
than  the  western. 

281.  Here  indeed  resides   the   difficulty    of  getting 
along  the  eastern  side  of  the  Mer  de  Glace  :  a  difficulty 


112  THE  FORMS  OF   WATER  IN 

which,  was  one  reason  for  our  crossing  the  glacier 
opposite  to  the  Montanvert.  There  are  two  convex 
sweeps  on  the  eastern  side  to  one  on  the  western  side, 
hence  on  the  whole  the  eastern  side  of  the  Mer  de  Glace 
is  most  riven . 

§  43.  Moraine-ridges,  Glacier  Tables,  and  Sand  Cones. 

282.  When  you  and  I  first  crossed  the  Mer  de  Glace 
from  Trelaporte  to  the  Couvercle,  we  found  that  the 
stripes   of  rocks  and   rubbish  which    constituted   the 
medial  moraines  were  ridges  raised  above  the  genera] 
level  of  the  glacier  to  a  height  at  some  places  of  twenty 
or  thirty  feet.     On  examining  these  ridges  we  found  the 
rubbish  to  be  superficial,  and  that  it  rested  upon  a  great 
spine  of  ice  which  ran  along  the  back  of  the  glacier. 
By  what  means  has  this  ridge  of  ice  been  raised  ? 

283.  Most  boys  have  read  the  story  of  Dr.  Franklin's 
placing  bits  of  cloth  of  various  colours  upon  snow  on  a 
sunny  day.     The  bits  of  cloth  sank  in  the  snow,  the 
dark  ones  most. 

284.  Consider  this  experiment.     The  sun's  rays  first 
of  all  fall  upon  the  upper  surface  of  the  cloth  and  warm 
it.     The  heat  is  then  conducted  through  the  cloth  to 
the  under  surface,  and  the  under  surface  parses  it  on  to 
the  snow,  which  is  finally  liquefied  by  the  heat.     It  is 
quite  manifest  that  the  quantity  of  snow  melted  will 
altogether  depend  upon  the  amount  of  heat  sent  from 
the  upper  to  the  under  surface  of  the  cloth. 


CLOUDS  AND  KIVEKS,  ICE  AND  GLACIERS.         113 

285.  Now  cloth  is  what  is  called  a  bad  conductor. 
It  does  not  permit  heat  to   travel  freely  through  it. 
But  where  it  has  merely  to  pass  through  the  thickness 
of  a  single  bit  of  cloth,  a  good  quantity  of  the  heat 
gets  through.     But  if  you  double  or  treble  or  quintuple 
the  thickness  of  the  cloth ;  or,  what  is  easier,  if  you  put 
several  pieces  one  upon  the  other,  you  come  at  length 
to  a  point  where  110  sensible  amount  of  heat  could  get 
through  from  the  upper  to  the  under  surface. 

286.  What  must  occur  if  such  a  thick  piece,  or  such 
a  series  of  pieces  of  cloth,  were  placed  upon  snow  on 
which  a  strong  sun  is  falling?     The  snow  round  the 
cloth  is  melted,  but  that  underneath  the  cloth  is  pro- 
tected.    If  the   action  continue  long  enough  the  in- 
evitable result  will  be,  that  the  level  of  the  snow  all 
round  the  cloth  will  sink,  and  the  cloth  will  be  left 
behind  perched  upon  an  eminence  of  snow. 

287.  If  you  understand  this,  you  have  already  mastered 
!  the  cause  of  the  moraine-ridges.    They  are  not  produced 

by  any  swelling  of  the  ice  upwards.  But  the  ice  under- 
neath the  rocks  and  rubbish  being  protected  from 
the  sun,  the  glacier  right  and  left  melts  away  and  leaves 
a  ridge  behind.  ~~\ 

288.  Yarious  other  appearances  upon  the  glacier  are 
accounted  for  in  the  same  way.  jJSere  upon  the  Mer  de 
Glace  we  have  flat  slabs  of  rock  sometimes  lifted  up  on 
pillars  of  ice.     These  are  the  so-called  Glacier  Tables. 
They  are  produced,  not  by  the  growth  of  a  stalk  of  ice 


114  THE  EORMS  OE  WATER  IN 

out  of  the  glacier,  but  by  the  melting  of  the  glacier  all 
round  the  ice  protected  by  the  stoneT\  Here  is  a  sketch 
of  one  of  the  Tables  of  the  Mer  de  Glace. 


289.  Notice  moreover  that  a  glacier  table  is  hardly  ever 
set  square  upon  its  pillar.     It  generally  leans  to  one 
side,  and  repeated  observation  teaches  you  that  it  so 
leans  as  to  enable  you  always  to  draw  the  north  and 
south  line  upon  the  glacier.     For  the  sun  being  south 
of  the  zenith  at  noon  pours  its  rays  against  the  south- 
ern end  of  the  table,  while  the  northern  end  remains  in 
shadow.      The    southern    end,   therefore,   being   most 
warmed  does  not  protect  the  ice  underneath  it  so  effec- 
tually as  the  northern  end.    The  table  becomes  inclined, 
and  ends  by  sliding  bodily  off  its  pedestal. 

290.  In  the  figure  opposite  we  have  what  may  be  called 


CLOUDS  AND   RIVERS,   ICE  AND  GLACIERS. 


115 


an  ideal  Table.  The  oblique  lines  represent  the  direction 
of  the  sunbeams,  and  the  consequent  tilting  of  the  table 
here  shown  resembles  that  observed  upon  the  glaciers. 

291.  A  pebble   will   not   rise  thus  :    like  Franklin's 
single  bit  of  cloth,  a  dark-coloured  pebble  sinks  in  the 
ice.     A  spot  of  black  mould  will  not  rest  upon  the  sur- 
face, but  will  sink  ;  and  various  parts  of  the  Glacier  du 
Geant  are  honeycombed  by  the  sinking  of  such  spots  of 
dirt  into  the  ice. 

292.  But  when  the  dirt  is  of  a  thickness  sufficient  to 
protect  the  ice  the  case  is  different.      Sand  is  often 


washed  away  by  a  stream  from  the  mountains,  or  from 
the  moraines,  and  strewn  over  certain  spaces  of  the 
glacier.  A  most  curious  action  follows :  the  sanded 


116  THE  FOEMS  OF  WATER  IN 

surface  rises,  the  part  on  which  the  sand  lies  thickest 
rising  highest.  Little  peaks  and  eminences  jut  forth, 
and  when  the  distribution  of  the  sand  is  favourable, 
and  the  action  sufficiently  prolonged,  you  have  little 
mountains  formed,  sometimes  singly,  and  sometimes 
grouped  so  as  to  mimic  the  Alps  themselves.  The  Sand 
Cones  of  the  Mer  de  Glace  are  not  striking;  but  on 
the  Gorner,  the  Aletsch,  the  Morteratsch,  and  other 
glaciers,  they  form  singly  and  in  groups,  reaching 
sometimes  a  height  of  ten  or  twenty  feet. 

§  44.   The  Glacier  Mills  or  Moulins. 

293.  You  and  I  have  learned  by  long  experience  the 
character  of  the  Mer  de  Glace.     We  have  marched  over 
it  daily,  with  a  definite  object  in  view,  but  we  have 
not  closed  our  eyes  to  other  objects.     It  is  from  side 
glimpses  of  things  which  are  not  at  the  moment  occu- 
pying our  attention  that  fresh  subjects  of  enquiry  arise 
in  scientific  investigation. 

294.  Thus  in  marching  over  the  ice  near  Trelaporte 
we  were  often  struck  by  a  sound  resembling  low  rumbling 
thunder.     We  subsequently  sought  out  the  origin  of 
this  sound,  and  found  it. 

295.  A  large  area  of  this  portion  of  the  glacier  is 
unbroken.     Driblets  of  water  have  room  to  form  rills ; 
rills  to  unite  and  form  streams  ;  streams  to  combine  to 
form  rushing  brooks,  which  sometimes  cut  deep  chan- 
nels in  the  ice.     Sooner  or  later  these  streams  reach  a 


CLOUDS  AND  EIVEKS,   ICE  AND   GLACIERS.          117 

strained  portion  of  the  glacier,  where  a  crack  is  formed 
across  the  stream.  A  way  is  thus  opened  for  the  water 
to  the  bottom  of  the  glacier.  By  long  action  the  stream 
hollows  out  a  shaft,  the  crack  thus  becoming  the 
starting-point  of  a  funnel  of  unseen  depth,  into  which 
the  water  leaps  with  the  sound  of  thunder. 

296.  This  funnel  and  its  cataract  form  a  glacier  Mill 
or  Moulin. 

297.  Let  me  grasp  your  hand  firmly  while  you  stand 
upon  the  edge  of  this  shaft  and  look  into  it.     The  hole, 
with  its  pure  blue  shimmer,  is  beautiful,  but  it  is  terrible. 
Incautious  persons   have   fallen   into   these   shafts,    a 
second  or  two  of  bewilderment  being  followed  by  sudden 
death.     But  caution  upon  the  glaciers  and  mountains 
ought,  by  habit,  to  be  made  a  second  nature  to  explorers 
like  you  and  me. 

298.  The  crack  into  which  the  stream  first  descended 
to  form  the  moulin,  moves  down  with  the  glacier.     A 
succeeding  portion  of  the  ice  reaches  the  place  where 
the  breaking  strain  is  exerted.     A  new  crack  is  then 
formed  above  the  moulin,  which   is   thenceforth  for- 
saken by  the  stream,  and  moves  downward  as  an  empty 
shaft.     Here  upon  the  Mer  de  Glace,  in  advance  of  the 
Grand  Moulin,  we  see  no  less  than  six  of  these  forsaken 
holes.     Some  of  them  we  sound  to  a  depth  of  90  feet. 

299.  But  you  and  I  both  wish  to  determine,  if  possible, 
the  entire  depth  of  the  Mer  de  Glace.     The  Grand 
Moulin  offers  a  chance  of  doing  this  which  we  must  not 


118  THE  FORMS  OF  WATER  IN 

neglect.  Our  first  effort  to  sound  the  mouliii  fails 
through  the  breaking  of  our  cord  by  the  impetuous 
plunge  of  the  water.  A  lump  of  grease  in  the  hollow 
of  a  weight  enables  a  mariner  to  judge  of  a  sea  bottom. 
We  employ  such  a  weight,  but  cannot  reach  the  bed  of 
the  glacier.  A  depth  of  163  feet  is  the  utmost  reached 
by  our  plummet. 

300.  From  July  28  to  August  8  we  have  watched  the 
progress  of  the  Grand   Moulin.     On  the   former  date 
the  position  of  the  Moulin  was  fixed.     On  the  31st  it 
had  moved  down  50  inches ;  a  little  more  than  a  day 
afterwards  it  had  moved  74  inches.     On  August  8  it 
had  moved  198  inches,  which  gives  an  average  of  about 
18  inches  in  twenty -four  hours.     No  doubt  next  summer 
upon  the  Mer  de  Glace  a  Grand  Moulin  will  be  found 
thundering  near  Trelaporte;  but  like  the  crevasse  of 
the  Grand  Plateau,  already  referred  to  (§  16),  it  will 
not  be  our  Moulin.     This,  or  rather  the  ice  which  it 
penetrated,  is  now   probably  more  than  a  mile  lower 
down  than  it  was  in  1857. 

§  45.  The  Changes  of  Volume  of  Water  ly  Heat  and  Cold. 

301.  We  have  noticed  upon  the  glacier  shafts  and 
pits    filled    with   water    of    the   most    delicate    blue. 
In  some  cases  these  have  been  the  shafts  of  extinct 
moulins    closed   at  the   bottom.     A   theory  has  been 
advanced  to  account  for  them,  which,  though  it  may 
be  untenable,  opens  out  considerations  regarding  the 


CLOUDS  AND  EIVEKS,  ICE  AND  GLACIERS.          119 

properties  of  water  that  ought  to  be  familiar  to  enquirers 
like  you  and  me. 

302.  In  our  dissection  of  lake  ice  by  a  beam  of  heat 
(§  11)  we  noticed  little  vacuous  spots  at  the  centres  of 
the  liquid  flowers  formed  by  the  beam.     These  spots  we 
referred  to  the  fact  that  when  ice  is  melted  the  water 
produced  is  less  in  volume  than  the  ice,  and  that  hence 
the  water  of  the  flower  was  not  able  to  occupy  the  whole 
space  covered  by  the  flower. 

303.  Let  us  more  fully  illustrate  this  subject.     Stop 
a  small  flask  water-tight  with  a  cork,  and  through  the 
cork  introduce  a  narrow  glass  tube  also  water-tight. 
It  is  easy  to  fill  the  flask  with  water  so  that  the  liquid 
shall  stand  at  a  certain  height  in  the  glass  tube. 

304.  Let  us  now  warm,  the  flask  with  the  flame  of  a 
spirit-lamp.     On  first   applying  the   flame  you   notice 
a  momentary  sinking  of  the  liquid  in  the  glass  tube. 
This  is  due  to  the  momentary  expansion  of  the  flask 
by  heat ;  it  becomes  suddenly  larger  when  the  flame 
is  first  applied. 

305.  But  the  expansion  of  the  water  soon  overtakes 
that  of  the  flask  and  surpasses  it.     We  immediately  see 
the  rise  of  the  liquid  column  in  the  glass  tube,  exactly 
as  mercury  rises  in  the  tube  of  a  warmed  thermometer. 

306.  Our  glass  tube  is  ten  inches  long,  and  at  starting 
the  water  stood  in  it  at  a  height  of  five  inches.     We 
will  apply  the  spirit-lamp  flame  until  the  water  rises 
quite  to  the  top  of  the  tube  and  trickles  over.     This 


120  THE  FORMS  OF  WATER  IN 

experiment  suffices  to  show  the  expansion  of  the  water 
by  heat. 

307.  We  now  take  a  common  finger-glass  and  put 
into  it  a  little  pounded  ice  and  salt.     On  this  we  place 
the  flask,  and  then  build  round  it  the  freezing  mixture. 
The  liquid  column  retreats  down  the  tube,  proving  the 
contraction  of  the  liquid  by  cold.    We  allow  the  shrinking 
to  continue  for  some  minutes,  noticing  that  the  down- 
ward retreat  of  the  liquid  becomes  gradually  slower, 
and  that  it  finally  ceases  altogether. 

308.  Keep   your   eye   upon    the   liquid   column;    it 
remains  quiescent  for  a  fraction  of  a  minute,  and  then 
moves   once    more.     But   its  motion   is   now   upwards 
instead  of  downwards.     The  freezing  mixture  now  acts 
exactly  like  the  flame. 

309.  It  would  not  be  difficult  to  pass  a  thermometer 
through  the  cork  into  the  flask,  and  it  would  tell  us  the 
exact  temperature  at  which  the  liquid  ceased  to  contract 
and  began  to  expand.     At  that  moment  we  should  find 
the  temperature  of  the  liquid  a  shade  over  39°  Fahr. 

310.  At  this  temperature,  then,  water  attains  its  maxi- 
mum density. 

311.  Seven  degrees  below  this  temperature,  or  at  32° 
Fahr.,  the  liquid  begins  to  turn  into  solid  crystals  of  ice, 
which  you  know  swims  upon  water  because  it  is  bulkier 
for  a  given  weight.     In  fact,  this  halt  of  the  approach  ing 
molecules  at  the  temperature  of  39°,  is  but  the  prepara- 
tion for  the  subsequent  act  of  crystallisation,  in  which 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIEES.          121 

the  expansion  by  cold  culminates.  Up  to  the  point  of 
solidification  the  increase  of  volume  is  slow  and  gradual ; 
•while  in  the  act  of  solidification  it  is  sudden,  and  of 
overwhelming  strength. 

312.  By  this  force  of  expansion  the  Florentine  Acade- 
micians long  ago  burst  a  sphere  of  copper  nearly  three 
quarters  of  an  inch  in  thickness.     By  the  same  force 
the  celebrated  astronomer  Huyghens  burst  in  1667  iron 
cannons    a  finger   breadth   thick.       Such  experiments 
have   been  frequently   made  since.      Major  Williams 
during  a  severe   Quebec  winter  filled  a   mortar  with 
water,  and  closed  it  by  driving  into  its  muzzle  a  plug 
of  wood.     Exposed  to  a  temperature  50°  Fahr.  below 
the   freezing    point   of  water,  the  metal  resisted  the 
strain,   but  the  plug  gave  way,  being  projected  to  a 
distance    of   400  feet.      At   Warsaw   howitzer    shells 
have  been  thus  exploded ;  and  you  and   I  have   shi- 
vered thick  bomb-shells  to  fragments,  by  placing  them 
for  half  an  hour  in  a  freezing  mixture. 

313.  The  theory  of  the  shafts  and  pits  referred  to 
at  the  beginning  of  this  section  is  this : — The  water 
at  the  surface  of  the  shaft  is  warmed  by  the  sun,  say  to 
a  temperature  of  39°  Fahr.     The  water  at  the  bottom, 
in  contact  with  the  ice,  must  be  at  32°  or  near  it.     The 
heavier  water  is  therefore  at  the  top ;  it  will  descend 
to  the  bottom,  melt  the  ice  there,  and  thus  deepen  the 
shaft. 

314.  The  circulation  here   referred  to  undoubtedly 


L22  THE  FORMS  OP  WATER  IN 

goes  on,  and  some  curious  effects  are  due  to  it ;  but 
not,  I  think,  the  one  here  ascribed  to  it.  The  deepening 
of  a  shaft  implies  a  quicker  melting  of  its  bottom  than 
of  the  s'urface  of  the  glacier.  It  is  not  easy  to  see  how 
the  fact  of  the  solar  heat  being  first  absorbed  bj  water, 
and  then  conveyed  by  it  to  the  bottom  of  the  shaft, 
should  make  the  melting  of  the  bottom  more  rapid  than 
that  of  the  ice  which  receives  the  direct  impact  of 
the  solar  rays.  The  surface  of  the  glacier  must  sink 
at  least  as  rapidly  as  the  bottom  of  the  pit,  so  that 
the  circulation,  though  actually  existing,  cannot  produce 
the  effect  ascribed  to  it. 


§  46.  Consequences  flowing  from  the  foregoing  Properties 
of  Water.     Correction  of  Errors. 

315.  I   was    not   much   above   your   age   when  the 
property  of  water   ceasing   to  contract   by  cold  at  a 
temperature  of  39°  Fahr.  was  made  known  to  me,  and  I 
still  remember  the  impression  it  made  upon  me.     For 
I  was  asked  to  consider  what  would  occur  in  case  this 
solitary  exception  to  an  otherwise  universal  law  ceased 
to  exist. 

316.  I  was  asked  to  reflect  upon  the  condition  of  a 
lake  stored  with  fish  and  offering  its  surface  to  very 
cold  air.     It  was  made  clear  to  me  that  the  water  on 
being  first  chilled  would  shrink  in  volume  and  become 
heavier,  that  it  would  therefore  sink  and  have  its  place 


CLOUDS  AND  KIVEES,  ICE  AND   GLACIEES.         123 

supplied  by  the  warmer  and  lighter  water  from  the 
deeper  portions  of  the  lake. 

317.  It  was  pointed  out  to  me  that  without  the  law 
referred  to  this  process  of  circulation  would  go  on  until 
the  whole  water  of  the  lake  had  been  lowered  to  the 
freezing  temperature.     Congelation  would  then  begin, 
and  would  continue  as  long  as  any  water  remained  to  be 
solidified.    One  consequence  of  this  would  be  to  destroy 
every  living  thing  contained  in  the  lake.  Other  calamities 
were  added,  all  of  which  were  said  to  be  prevented  by 
the  perfectly  exceptional  arrangement,  that  after  a  cer- 
tain time  the  colder  water  becomes  the  lighter,  floats 
on  the  surface  of  the  lake,   is  there  congealed,  thus 
throwing  a  protecting  roof  over  the  life  below. 

318.  Count  Rumford,  one  of  the  most  solid  of  scientific 
men,  writes  in  the  following  strain  about  this  question  : 
— '  It  does  not  appear  to  me  that   there  is   anything 
which  human  sagacity  can  fathom,  within  the  wide- 
extended  bounds  of  the  visible  creation,  which  affords  a 
more  striking  or  more  palpable  proof  of  the  wisdom  of 
the  Creator,  and  of  the  special  care  He  has  taken  in  the 
general  arrangement  of  the  universe,  to  preserve  animal 
life,  than  this  wonderful  contrivance. 

319.  '  Let  me  beg  the  attention  of  my  readers  while  I 
endeavour  to  investigate  this  most  interesting  subject ; 
and  let  me  at  the  same  time  bespeak  his  candour  and 
indulgence.     I  feel  the  danger  to  which  a  mortal  ex- 
poses himself  who  has  the  temerity  to  explain  the  designs 


124  THE  FOEMS  OF   WATEE  IN 

of  Infinite  Wisdom.     The   enterprise  is   adventurous, 
but  it  surely  cannot  be  improper. 

320.  '  Had  not  Providence  interfered  on  this  occasion 
in  a  manner  which  may  well  be  considered  as  miracu- 
lous, all  the  fresh  water  within  the  polar  circle  must 
inevitably  have  been  frozen  to  a  very  great  depth  in 
winter,  and  every  plant  and  tree  destroyed.' 

321.  Through  many  pages  of  his  book  Count  Rumford 
continues  in  this  strain  to  expound  the  ways  and  in- 
tentions of  the  Almighty,  and  he  does  not  hesitate  to 
apply  very  harsh  words  to  those  who  cannot  share  his 
notions.     He  calls  them  hardened  and  degraded.     We 
are  here  warned  of  the  fact,  which  is  too  often  for- 
gotten, that  the  pleasure  or  comfort  of  a  belief,  or  the 
warmth  or  exaltation  of  feeling  which  it  produces,  is  no 
guarantee  of  its  truth.     For  the  whole  of  Count  Rum- 
ford's  delight  and  enthusiasm  in  connexion  with  this 
subject,  and  the  whole  of  his  ire  against  those  who  did 
not  share  his  opinions,  were  founded  upon  an  erroneous 
notion. 

322.  Water  is  not  a  solitary  exception  to  an  otherwise 
general  law.     There  are  other  molecules  than  those  of 
this  liquid  which  require  more  room  in  the  solid  crys- 
talline condition  than  in  the  adjacent  molten  condition. 
Iron  is  a  case  in  point.     Solid  iron  floats  upon  molten 
iron  exactly  as  ice  floats  upon  water.    Bismuth  is  a  still 
more  impressive  case,  and  we  could  shiver  a  bomb  as 
certainly  by  the  solidification  of  bismuth  as  by  that 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.         125 

of  water.     There  is  no  fish  to  be  taken  care  of  here, 
still  the  '  contrivance  '  is  the  same. 

323.  I  ana  reluctant  to  mention  them  in  the  same 
breath  with  Count  Rumford,  but  I  am  told  that  in  our 
own  day  there  are  people  who  profess  to  find  the  comforts 
of  a  religion  in  a  superstition  lower  than  any  that  has 
hitherto  degraded  the  civilized  human  mind.    So  that 
the  happiness  of  a  faith  and  the  truth  of  a  faith  are  two 
totally  different  things. 

324.  Life  and  the  conditions  of  life  are  in  necessary 
harmony.     This  is  a  truism,  for  without  the  suitable 
conditions  life  could  not  exist.     But  both  life  and  its 
conditions  set  forth  the  operations  of  inscrutable  Power. 
We  know  not  its  origin ;  we  know  not  its  end.     And 
the   presumption,  if  not  the   degradation,  rests   with 
those  who  place  upon  the   throne   of  the   universe   a 
magnified  image  of  themselves,  and  make  its  doings 
a  mere  colossal  imitation  of  their  own. 

§  47.   The  Molecular  Mechanism  of  Water-congelation. 

325.  But  let  us  return  to  our  science.     How  are  we 
to  picture  this  act  of  expansion  on  the  part  of  freezing 
water  ?     By  what  operation  do  the  molecules  demand 
with  such  irresistible  emphasis  more  room  in  the  solid 
than  in  the  adjacent  liquid  condition  ?     In  all  cases  of 
this  kind   we   must  derive  our  conceptions  from   the 
world  of  the  senses,  and  transfer  them  afterwards  to  a 
world  transcending  the  range  of  the  senses. 


126  THE  FOKMS  OF  WATER  IN 

326.  You  Lave  not  forgotten  our  conversation  re- 
garding  c  atomic  poles '   (§    10),  and  how  the  notion 
of  polar  force  came  to  be  applied  to  crystals.     With 
this  fresh  in  your  memory,  you  will  have  no  great  diffi- 
culty in  understanding  how  expansion  of  volume  may 
accompany  the  act  of  crystallisation. 

327.  I  place  a  number  of  magnets  before  you.     They, 
as  matter,  are  affected  by  gravity,  and,  if  perfectly  free, 
they  would  move  towards  each  other  in  obedience  to 
the  attraction  of  gravity. 

328.  But   they   are   not  only  matter,  but   magnetic 
matter.     They  not  only  act  upon  each  other  by  the 
simple   force   of    gravity,   but  by  the   polar  force   of 
magnetism.     Imagine  them  placed  at  a  distance  from 
each  other,  and  perfectly  free  to  move.     Gravity  first 
makes  itself  felt  and  draws  them  together.     For  a  time 
the  magnetic  force  issuing  from  the  poles  is  insensible  ; 
but  when  a  certain  nearness  is  attained,  the  polar  force 
comes  into  play.     The  mutually  attracting  points  close 
up,  the  mutually  repellent  points  retreat,  and  it  is  easy 
to  see  that  this  action  may  produce  an  arrangement  of 
the  magnets  which  requires  more  room.     Suppose  them 
surrounded  by  a  box  which  exactly  encloses  them  at 
the  moment  the  polar  force  first  comes  into  play.     It 
is  easy  to  see  that  in  arranging  themselves  subsequently 
the  repelled  corners  and  ends  of  the  magnets  may  be 
caused  to  press  against  the  sides  of  the  box,  and  even 
to  burst  it,  if  the  forces  be  sufficiently  strong. 


CLOUDS  AND  EIVEES,  ICE  AND  GLACIEKS.         127 

329.  Here  then  we  have  a   conception  which  may 
be  applied  to  the  molecules  of  water.      They,  like  the 
magnets,  are  acted  upon  by  two  distinct  forces.     Tor  a 
time  while  the  liquid  is   being  cooled  they  approach 
each  other,  in  obedience  to  their  general  attraction  for 
each  other.     But  at  a  certain  point  new  forces,  some 
attractive,  some  repulsive,  emanating  from  special  points 
of  the  molecules,  come  into  play.     The  attracted  points 
close  up,  the  repelled  points  retreat.     Thus  the  mole- 
cules turn  and  rearrange   themselves,   demanding,  as 
they  do  so,  more  space,  and  overcoming  all  ordinary 
resistance  by  the  energy  of  their  demand.     This,  in 
general  terms,  is  an  explanation  of  the  expansion  of 
water  in  solidifying :  it  would  be  easy  to  construct  an 
apparatus  for  its  illustration. 

§  48.  The  Dirt  Bands  of  the  Her  de  Glace. 

330.  Pass  from  bright  sunshine   into   a  moderately 
lighted  room ;  for  a  time  all  appears  so  dark  that  the 
objects  in  the  room  are  not  to  be  clearly  distinguished. 
Hit  violently  by  the  waves  of  light  (§  3)  the  optic  nerve 
is  numbed,  and  requires  time  to  recover  its  sensitiveness. 

331.  It  is  for  this  reason  that  I  choose  the  present 
hour  for  a  special  observation  on  the  Mer  de  Glace. 
The  sun  has  sunk  behind  the  ridge  of  Charmoz,  and  the 
surface  of  the  glacier  is  in  sober  shade.      The  main 
portion  of  our  day's  work  is  finished,  but  we  have  still 
sufficient  energy  to  climb  the  slopes  adjacent  to   the 

7 


128 


THE  FORMS  OF  WATER  IN 


Montanvert  to  a  height  of  a  thousand  feet  or  thereabouts 
above  the  ice. 

332.  We  now  look  fairly  down  upon  the  glacier,  and 


see  it  less  foreshortened  than  from  the  Montanvert.   We 
notice  the  dirt  overspreading  its  eastern  side,  due  to 


CLOUDS  AND  RIVERS,   ICE  AND  GLACIERS.         129 

the  crowding  together  of  its  medial  moraines.  We  see 
the  comparatively  clean  surface  of  the  Glacier  du 
Geant ;  but  we  notice  upon  this  surface  an  ap- 
pearance which  we  have  not  hitherto  seen.  It  is 


crossed  by  a  series  of  grey  bent  bands,  which  follow 
each  other  in  succession,  from  Trelaporte  downwards. 
We  count  eighteen  of  these  from  our  present  position. 
(See  sketch,  page  128.) 


130 


THE  FORMS   OF  WATER  IN 


333.  These  are  the  Dirt  Bands  of  the  Mer  de  Glace ; 
they  were  first  observed  by  Professor  Forbes  in  1842. 

334.  They  extend  down  the  glacier  further  than  we 
can  see ;  and  if  we  cross  the  valley  of  Chamouni,  and 


climb  the  mountains  at  the  opposite  side,  to  a  point 
near  the  little   auberge,  called  La  Flegere,  we   shall 


CLOUDS  AND  KIVERS,  ICE  AND   GLACIERS.         131 

command  a  view  of  the  end  of  the  glacier  and  observe  the 
completion  of  the  series  of  bands.  We  notice  that  they 
are  confined  throughout  to  the  portion  of  the  glacier 
derived  from  the  Col  du  Geant.  (See  sketch,  page  129.) 

335.  We   must  trace   them   to   their   source.     You 
know  how  noble  and  complete  a  view  is  obtained  of  the 
glacier  and  Col  du  Geant  from  the  Cleft  Station  above 
Trelaporte.     Thither  we  must  once  more  climb;  and 
thence  we  can  see  the  succession  of  bands  stretching 
downwards  to  the  Mon  tan  vert,  and  upwards  to  the  base 
of  the  ice-cascade  upon  the  Glacier  du  Geant.     The 
cascade  is  evidently  concerned  in  their  formation.     (See 
sketch  opposite.) 

336.  And  how?     Simply   enough.     The  glacier,  as 
we  know,  is  broken  transversely  at  the  summit  of  the 
ice-fall,  and  descends  the  declivity  in  a  series  of  great 
transverse  ridges.     At  the  base  of  the  fall,  the  chasms 
arc    closed,   but   the   ridges   in   part  remain   forming 
protuberances,   which  run    like   vast   wrinkles   across 
the  glacier.     These  protuberances  are  more  and  more 
bent  because  of  the  quicker  motion  of  the  centre,  and 
the  depressions  between  them  form  receptacles  for  the 
fine  mud  and  debris  washed  by  the  little  rills  from  the 
adjacent  slopes. 

337.  The  protuberances  sink  gradually  through  the 
wasting  action  of  the  sun,  so  that  long  before  Trelaporte 
is  reached  they  have  wholly  disappeared.     Not  so  the 
dirt  of  which  they  were  the  collectors  :  it  continues  to 


132  THE  FOEMS   OF  WATEK  IN 

occupy,  in  transverse  bands,  the  flat  surface  of  the  gla- 
cier. At  Trelaporte,  moreover,  where  the  valley  becomes 
narrow,  the  bands  are  much  sharpened,  obtaining  there 
the  character  which  they  afterwards  preserve  through- 
out the  Mer  de  Glace.  Other  glaciers  with  cascades 
also  exhibit  similar  bands. 

§  49.  Sea  Ice  and  Icebergs. 

338.  We  are  now  equipped  intellectually  for  a  cam- 
paign into  another  territory.     Water  becomes  heavier 
and  more  difficult  to  freeze  when  salt  is  dissolved  in  it. 
Sea  water  is   therefore  heavier    than   fresh,   and  the 
Greenland  Ocean  requires  to   freeze  it  a  temperature 
3^  degrees  lower  than  fresh  water.    When  concentrated 
till  its  specific  gravity  reaches  1*1045,  sea  water  re- 
quires for  its  congelation  a  temperature  18 £  degrees 
lower  than  the  ordinary  freezing-point.* 

339.  But  even  when  the  water  is  saturated  with  salt, 
the  crystallising  force  studiously  rejects  the  salt,  and 
devotes  itself  to  the  congelation  of  the  water  alone. 
Hence  the  ice  of  sea   water,  when  melted,   produces 
fresh  water.     The  only  saline  particles  existing  in  such 
ice  are  those  entangled  mechanically  in  its  pores.  They 
have  no  part  or  lot  in  the  structure  of  the  crystal. 

340.  This  exclusivenessy  if  I  may  use  the  term,  of  the 
water  molecules ;    this  entire  rejection  of  all  foreign 

*  Scoresby. 


CLOUDS  AND  KIVEES,  ICE  AND  GLACIERS.          133 

elements  from  the  edifices  which  they  build,  is  enforced 
to  a  surprising  degree.  Sulphuric  acid  has  so  strong 
an  affinity  for  water  that  it  is  one  of  the  most  powerful 
agents  known  to  the  chemist  for  the  removal  of  humidity 
from  air.  Still,  as  shown  by  Faraday,  when  a  mixture 
of  sulphuric  acid  and  water  is  frozen,  the  crystal  formed 
is  perfectly  sweet  and  free  from  acidity.  The  water 
alone  has  lent  itself  to  the  crystallising  force. 

341.  Every  winter  in    the  Arctic   regions   the   sea 
freezes,  roofing  itself  with  ice  of  enormous  thickness 
and  vast  extent.     By  the  summer  heat,  and  the  tossing 
of  the  waves,  this  is  broken  up ;    the  fragments  are 
drifted  by  winds  and  borne  by  currents.     They  clash, 
they  crush  each  other,  they  pile  themselves  into  heaps, 
thus   constituting    the  chief    danger    encountered  by 
mariners  in  the  polar  seas. 

342.  But  among  the  drifting  masses  of  flat  sea-ice, 
vaster  masses  sail,  which  spring  from  a  totally  different 
source.     These  are  the  Icebergs  of  the  Arctic  seas.     They 
rise  sometimes  to  an  elevation  of  hundreds  of  feet  above 
the  water,  while  the  weight  of  ice  submerged  is  about 
seven  times  that  seen  above. 

343.  The  first  observers  of  striking  natural  pheno- 
mena  generally  allow   wonder   and  imagination  more 
than  their  due  place.     But  to  exclude  all  error  arising 
from  this  cause,  I  will  refer  to  the  journal  of  a  cool  and 
intrepid  Arctic  navigator,  Sir  Leopold  McClintock.     He 
describes  an  iceberg  250  feet  high,  which  was  aground 


134  THE  FOEMS  OF  WATEE  IN 

in  500  feet  of  water.  This  would  make  the  entire 
height  of  the  berg  750  feet,  not  an  unusual  altitude  for 
the  greater  icebergs. 

344.  From  Baffin's  Bay  these   mighty  masses  come 
sailing  down  through   Davis'    Straits   into   the   broad 
Atlantic.     A  vast  amount  of  heat  is  demanded  for  the 
simple  liquefaction  of  ice  (§  48) ;  and  the  melting  of 
icebergs  is  on  this  account  so  slow,  that  when  large 
they  sometimes  maintain  themselves  till  they  have  been 
drifted  2000  miles  from  their  place  of  birth. 

345.  What   is   their   origin?     The   Arctic   glaciers. 
From  the  mountains  in  the  interior  the  indurated  snows 
slide   into   the  valleys    and  fill  them  with   ice.      The 
glaciers  thus  formed  move  like  the  Swiss  ones,  inces- 
santly downward.     But  the   Arctic  glaciers  reach  the 
sea,  enter  it,  often  ploughing  up  its  bottom  into  sub- 
marine moraines.     Undermined  by  the  lapping  of  the 
waves,  and  unable  to  resist  the  strain  imposed  by  their 
own  weight,   they  break   across,   and   discharge   vast 
masses  into  the  ocean.     Some  of  these  run  aground  on 
the  adjacent  shores,  and  often  maintain  themselves  for 
years.     Others  escape  southward,  to  be  finally  dissolved 
in  the  warm  waters  of  the  Atlantic.     The  first  engra- 
ving on  the  opposite  page  is  copied  from  a  photograph 
taken  by  Mr.  Bradford  during  a  recent  expedition  to  the 
Northern  seas.     The  second  represents  a  mass  of  ice 
upon  the  Glacier  des  Bossons.     Their  likeness  suggests 
their  common  origin, 


CLOUDS  AND  RIVERS,   ICE  AND   GLACIERS.        135 


136  THE  FOKMS   OF  WATEK  IN 

§  50.   The  jffiggischhorn,  the  Mdrgelin  See  and  its 
Icebergs. 

346.  I  am,  however,  unwilling  that  you  should  quit 
Switzerland  without  seeing  such  icebergs  as  it  can  show, 
and  indeed  there  are  other  still  nobler  glaciers  than  the 
Mer  de  Glace  with  which  you  ought  to  be  acquainted. 
In  tracing  the  Rhone  to  its  source,  you  have  already 
ascended  the  valley  of  the  Rhone.     Let  us  visit  it  again 
together ;  halt  at  the  little  town  of  Viesch,  and  go  from 
it  straight  up  to  the  excellent  hostelry  on  the  slope  of 
the  JEggischhorn.    This  we  shall  make  our  head-quarters 
while  we  explore  that  monarch  of  European  ice-streams, 
— the  great  Aletsch  glacier. 

347.  Including  the  longest  of  its  branches,  this  noble 
ice-river  is  about  twenty  miles  long,  while  at  the  middle 
of  its  trunk  it  measures  nearly  a  mile  and  a  quarter  from 
side  to  side.     The  grandest  mountains  of  the  Bernese 
Oberland,  the  Jungfrau,  the  Monch,  the  Trugberg,  the 
Aletschhorn,   the   Breithorn,    the    Gletscherhorn,   and 
many  another  noble  peak  and  ridge,  are  the  collectors 
of  its  neves.     From  three  great  valleys  formed  in  the 
heart  of  the  mountains  these  neves  are  poured,  uniting 
together  to  form  the  trunk  of  the  Aletsch  at  a  place 
named  by  a  witty  mountaineer,  the  ( Place  de  la  Concorde 
of  Nature.'     If  the  phrase  be  meant  to  convey  the  ideas 
of  tranquil  grandeur,  beauty  of  form,  and  purity  of  hue, 
it  is  well  bestowed. 


CLOUDS  AND  EIVERS,  ICE  AND  GLACIERS.          137 

348.  Our  hotel  is  not  upon  the  peak  of  the  -ZEggisch- 
horn,  but  a  brisk  morning  walk  soon  places  us  upon  the 
top.     Thence  we  see   the   glacier  like   a   broad  river 
stretching  upwards  to  the  roots  of  the  Jungfrau,  and 
downwards   past   the  Bel  Alp   towards  its  end.     Pro- 
longing the   vision  downwards,  we  strike  the  noblest 
mountain  group  in  all   the   Alps, — the   Dom   and   its 
attendant  peaks,  the  Matterhorn  and  the  Weisshorn. 
The  scene  indeed  is  one  of  impressive  grandeur,  a  mul- 
titude of  peaks  and  crests  here  unnamed  contributing 
to  its  glory. 

349.  But  low  down  to  our  right,  and  surrounded  by 
the   sheltering  mountains,  is  an  object  the  beauty  of 
which  startles  those  who  are  unprepared  for  it.     Yonder 
we  see  the  naked  side  of  the  glacier,  exposing  glistening 
ice-cliffs  sixty  or  seventy  feet  high.     It  would  seem  as 
if  the  Aletsch  here  were  engaged  in  the  vain  attempt 
to  thrust  an  arm  through  a  lateral  valley.     It  once  did 
so ;  but  the  arm  is  now  incessantly  broken  off  close  to 
the  body  of  the  glacier,  a  great  space  formerly  covered 
by  the  ice  being  occupied  by  its  water  of  liquefaction. 
A  lake   of  the   loveliest  blue   is  thus  formed,  which 
reaches  quite  to  the  base  of  the  ice-cliffs,  saps  them, 
as  the   Arctic  waves  sap  the  Greenland  glaciers,  and 
receives  from  them  the   broken  masses  which  it  has 
undermined.     As  we  look  down  upon  the  lake,  small 
icebergs  sail  over  the  tranquil  surface,  each  resembling 
a  snowy  swan  accompanied  by  its  shadow. 


138  THE  FOEMS  OF  WATEE  IN 

350.  This  is  the  beautiful  little  lake  of  Margelin,  or, 
as  the  Swiss  here  call  it,  the  Margelin  See.     You  see 
that  splash,  and  immediately  afterwards  hear  the  sound 
of  the  plunging  ice.     The  glacier  has  broken  before  our 
eyes,  and  dropped  an  iceberg  into  the  lake.     All  over 
the  lake  the  water  is  set  in  commotion,  thus  illustrating 
on  a  small  scale  the  swamping  waves  produced  by  the 
descent  of  vast  islands  of  ice  from  the  Arctic  glaciers. 
Look  to  the  end  of  the  lake.     It  is  cumbered  with  the 
remnants  of  icebergs  now  aground,  which  have  been  in 
part  wafted  thither  by  the  wind,  but  in  part  slowly  borne 
by  the  water  which  moves  gently  in  this  direction. 

351.  Imagine  us  below  upon  the  margin  of  the  lake, 
as  I  happened  to  be  on  one  occasion.     There  is  one 
large  and  lonely  iceberg  about  the  middle.     Suddenly 
a  sound  like  that  of  a  cataract  is  heard ;  we  look  towards 
the   iceberg    and   see   water  teeming   from   its   sides. 
Whence  comes  the  water?  the  berg  has  become  top- 
heavy  through  the  melting  underneath ;  it  is  in  the  act 
of  performing  a  somersault,  and  in  rolling  over  carries 
with  it  a  vast  quantity  of  water,  which  rushes  like  a 
waterfall  down  its  sides.     And  notice  that  the  iceberg, 
which  a  moment  ago  was  snowy-white,  now  exhibits  the 
delicate  blue  colour  characteristic  of  compact  ice.  It  will 
soon,  however,  be  rendered  white  again  by  the  action 
of  the  sun.     The  vaster  icebergs  of  the  Northern  seas 
sometimes  roll  over  in  the  same  fashion.     A  week  may 
be  spent  with  delight  and  profit  at  the  JEggischhorn. 


CLOUDS  AND  EIVERS,  ICE  AND  GLACIEKS.         139 

§  51.  The  Bel  Alp. 

352.  From  tlie  JEggischhorn  I  might  lead  you  along 
the  mountain  ridge  by  the  Betten  See,  the  fish  of  which 
we  have  already  tasted,  to  the  Rieder  Alp,  and  thence 
across  the  Aletsch  to  the  Bel  Alp.    This  is  a  fine  moun- 
tain ramble,  but  you  and  I  prefer  making  the  glacier 
our    highway   downwards.     Easy  at  some  places,  it  is 
by  no  means  child's  play  at  others  to  unravel  its  cre- 
vasses.   But  the  steady  constancy  and  close  observation 
which  we  have  hitherto  found  availing  in  difficult  places 
do  not  forsake  us  here.     We  clear  the  fissures ;  and, 
after  four  hours  of  exhilarating  work,  we  find  ourselves 
upon  the  slope  leading  up  to  the  Bel  Alp  hotel. 

353.  This  is  one  of  the  finest  halting-places  in  the 
Alps.     Stretching   before  us  up  to   the  JEggischhorn 
and  Margeliii  See  is  the  long  last  reach  of  the  Aletsch, 
with  its  great  medial  moraine  running  along  its  back. 
At  hand  is  the  wild  gorge  of  the  Massa,  in  which  the 
snout  of  the  glacier  lies  couched  like  the  head  of  a 
serpent.  The  beautiful  system  of  the  Oberaletsch  glaciers 
is  within  easy  reach.     Above  us  is  a  peak  called  the 
Sparrenhorn,  accessible  to  the  most  moderate  climber, 
and  on  the  summit  of  which  little  more  than  an  hour's 
exertion  will  place  you  and  me.     Below  us  now  is  the 
Oberaletsch  glacier,  exhibiting  the  most  perfect  of  medial 
moraines.     Near  us  is  the  great  mass  of  the  Aletsch- 
horn,  clasped  by  its  neves,  and  culminating  in  brown 


140  THE  FOEMS  OF  WATER  IN 

rock.  It  is  supported  by  other  peaks  almost  as  noble 
as  itself.  The  Nesthorn  is  at  hand ;  while  sweeping 
round  to  the  west  we  strike  the  glorious  triad  already 
referred  to,  the  Weisshorn,  the  Matterhorn,  and  the 
Dom.  Take  one  glance  at  the  crevasses  of  the  glacier 
immediately  below  us.  It  tumbles  at  its  end  down  a 
steep  incline,  and  is  greatly  riven.  But  the  crevasses 
open  before  the  steep  part  is  reached,  and  you  notice 
the  coalescence  of  marginal  and  transverse  crevasses, 
producing  a  system  of  curved  fissures  with  the  convex- 
ities of  the  curves  pointing  upwards.  The  mechanical 
reason  of  this  is  now  known  to  you.  The  glacier-tables 
are  also  numerous  and  fine.  I  should  like  to  linger 
with  you  here  for  a  week,  exploring  the  existing  glaciers, 
and  tracing  out  the  evidences  of  others  that  have  passed 
away. 

§  52.  The  Riffelberg  and  Gorner  Glacier. 

854.  And  though  our  measurements  and  observations 
on  the  Mer  de  Glace  are  more  or  less  representative  of 
all  that  can  be  made  or  solved  elsewhere,  I  am  unwilling 
to  leave  you  unacquainted  with  the  great  system  of 
glaciers  which  stream  from  the  northern  slopes  of 
Monte  Rosa  and  the  adjacent  mountains.  From  the 
Bel  Alp  we  can  descend  to  Brieg,  and  thence  drive  to 
Visp ;  but  you  and  I  prefer  the  breezy  heights,  so  we 
sweep  round  the  promontory  of  the  Nessel,  until  we 
stand  over  the  Rhone  valley,  in  front  of  Visp.  From 


CLOUDS  AND  RIVEKS    ICE  AND  GLACIERS.         141 

this  village  an  hour's  walking  carries  us  to  Stalden, 
where  the  valley  divides  into  two  branches :  the  one 
leading  through  Saas  over  the  Monte  Moro,  and  the 
other  through  St.  Nicholas  to  Zermatt.  The  latter  is 
our  route. 

355.  We  reach  Zermatt,  but  do  not  halt  there.     On 
the  mountain  ridge,  4,000  feet  above  the  valley,  we 
d iscern  the  Biffelberg  hotel.     This  we  reach.     Eight  in 
front  of  us  is  the  pinnacle  of  the  Matterhorn,  upon 
the   top  of  which   it   must   appear  incredible  to  you 
that  a  human  foot  could  ever  tread.     Constancy  and 
skill,  however,  accomplished  this,    but  in  the  first  in- 
stance  at   a  terrible   price.     In  the  little  churchyard 
of  Zermatt  we   have   seen  the  graves  of  two  of  the 
greatest  mountaineers  that  Savoy  and  England  have 
produced;    and  who,   with   two   gallant    young    com- 
panions, fell  from  the  Matterhorn  in  1865. 

356.  At  the  Riffelberg  we  are  within  an  hour's  walk 
of  the  famous  Gorner  Grat,  which  commands  so  grand 
a  view  of  the  glaciers  of  Monte  Rosa.    But  yonder  huge 
knob  of  perfectly  bare  rock,  which  is  called  the  Riffel- 
horn,  must  be  our  station.     What  the  Cleft  Station  is 
to  the  Mer  de  Glace,  the  Riffelhorn  is  to  the  Gorner 
glacier  and  its  tributaries.     From  its  lower  side  the 
rock,  easy  as  it  may  seem,  is  inaccessible.    Here,  indeed, 
in  1865,  a  fifth  good  man  met  his  end,  and  he  also  lies 
beside  his  fellow  countrymen  in  the  churchyard  of  Zer- 
matt.  Passing  a  little  tarn,  or  lake,  called  the  Eiffel  See, 


142  THE  FORMS  OF  WATER  IN 

we  assail  the  Eiffelhorn  on  its  upper  side.  It  is  capital 
rock-practice  to  reach  the  summit;  and  from  it  we 
command  a  most  extraordinary  scene. 

357.  The  huge  and   many-peaked   mass   of  Monte 
Eosa  faces  us,  and  we  scan  its  snows  from  bottom  to 
top.     To  the  right  is  the  mighty  ridge  of  the  Lyskamm, 
also   laden   with    snow;    and    between   both   lies   the 
Western  Glacier  of  Monte  Eosa.     This  glacier  meets 
another  from  the  vast  snow-fields  of  the  Cima  di  Jazzi ; 
they  join  to  form  the  Gorner  glacier,  and  from  their  place 
of  junction  stretches   the  customary  medial  moraine. 
On  this  side  of  the  Lyskamm  rise  two  beautiful  snowy 
eminences,  the  Twins  Castor  and  Pollux ;    then  come 
the  brown  crags  of  the  Breithorn,  then  the  Little  Mat- 
terhorn,  and  then  the  broad  snow- field  of  the  Theodule, 
out  of  which  springs  the  Great  Matterhorn,  and  which 
you  and  I  will  cross  subsequently  into  Italy. 

358.  The  valleys  and  depressions  between  these  moun- 
tains are  filled  with  glaciers.     Down  the  flanks  of  the 
Twin  Castor  comes  the  Glacier  des  Jumeaux,  from  Pollux 
comes  the  Schwartze  glacier,  from  the  Breithorn  the 
Trifti  glacier,  then  come  the  Little  Matterhorn  glacier 
and  the  Theodule  glacier,  each,  as  it  welds  itself  to  the 
trunk,  carrying  with  it  its  medial  moraine.     We  can 
count  nine   such  moraines  from  our   present  position. 
And  to  a  still  more  surprising  degree  than  on  the  Mer 
de  Glace,  we  notice  the  power  of  the  ice  to  yield  to 
pressure  ;  the  broad  neves  being  squeezed  on  the  trunk 


CLOUDS  AND  KIVERS,   ICE  AND  GLACIERS.         143 

of  the  Gorner  into  white  stripes,  which  become  ever 
narrower  between  their  bounding  moraines,  and  finally 
disappear  under  their  own  shingle. 

359.  On  the  two  main  tributaries  we  also  notice 
moraines  which  seem  in  each  case  to  rise  from  the 
body  of  the  glacier,  appearing  in  the  middle  of  the 


THE  CORNER  GLACIER,  WITH  MONTE  ROSA  IN  THE  DISTANCE,  AND  THE 
RIFFELHORN  TO  THE  LEFT. 

ice  without  any  apparent  origin  higher  up.  These 
at  their  sources,  are  sub-glacial  moraines,  which  have 
been  rubbed  away  from  rocky  promontories  entirely 
covered  with  ice.  They  lie  hidden  for  a  time  in  the 
body  of  the  glacier,  and  appear  at  the  surface  where 
the  ice  above  them  has  been  melted  away  by  the  sun. 


144  THE  FOKMS   OF  WATEE  IN 

360.  This  is   the  place  to  mention   a   notion   long 
entertained  by  the  inhabitants  of  the  high  Alps,  that 
glaciers  possess  the  power  of  thrusting  out  all  impu- 
rities  from   them.     On  the  Mer  de  Glace  you  and  I 
have  noticed  large  patches  of  clay  and  black  mud  which 
evidently  came  from  the  body  of  the  glacier,  and  we  can 
therefore  understand  how  natural  was  this  notion  of 
extrusion  to   people  unaccustomed  to  close  observation. 
But  the  power  of  the  glacier  in  this  respect  is  in  reality 
the  power  of  the  sun,  which  fuses  the  ice  above  con- 
cealed impurities,  and,  like  the  bodies  of  the  guides  on 
the  Glacier  des  Bossons  (143),  brings  them  to  the  light 
of  day. 

361.  On  no  other  glacier  will  you  find  more  objects 
of  interest  than  on  the  Gorner.     Sand  cones,  glacier- 
tables,  deep  ice  gorges  cut  by  streams  and  bridged  fan- 
tastically by  boulders,  moulins,  sometimes  arched  ice- 
caverns  of  extraordinary  size  and  beauty.    On  the  lower 
part  of  the  glacier  we  notice  the  partial  disappearance  of 
the  medial  moraine  in  the  crevasses,  and  its  reappear- 
ance at  the  foot  of  the  incline.     Tor  many  years  this 
glacier  was  steadily  advancing  on  the  meadow  in  front 
of  it,  ploughing  up  the  soil  and  overturning  the  chalets 
in  its  way.     It  now  shares  in  the  general  retreat  exhi- 
bited during  the  last  fifteen  years  among  the  glaciers 
of  the  Alps.     As  usual,  a  river,  the  Yisp,  rushes  from 
a  vault  at  the  extremity  of  the  Gorner  glacier. 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.          145 

§  53.  Ancient  Glaciers  of  Switzerland. 

362.  You    have   not  lost  the   memory   of    the   old 
Moraine,  which  interested  us  so  much  in  our  first  ascent 
from  the   source  of  the  Arveiron ;   for  it  opened  our 
minds  to  the  fact  that  at  one  period  of  its  history  the 
Mer  de  Glace  attained  far  greater  dimensions  than  it 
now   exhibits.     Our   experience    since    that   time  has 
enabled  us  to  pursue  these  evidences  of  ice  action  to  an 
extent  of  which  we  had  then  no  notion. 

363.  Close  to  the  existing  glacier,  for  example,  we 
have  repeatedly  seen  the  mountain  side  laid  bare  by  the 
retreat  of  the  ice.     This  is  especially  conspicuous  just 
now,  because  for  the  last  fifteen  or  sixteen  years  the 
glaciers  of  the  Alps  have  been  steadily  shrinking;  so 
that  it  is  no  uncommon  thing  to  see  the  marginal  rocks 
laid  bare  for  a  height  of  fifty,  sixty,  eighty,  or  even  one 
hundred  feet  above  the  present  glacier.     On  the  rocks 
thus  exposed  we  see  the  evident  marks  of  the  sliding ; 
and  our  eyes  and  minds  have  been  so  educated  in  the 
observation  of  these  appearances  that  we  are  now  able 
to  detect,  with  certainty,  icemarks,  or  moraines,  ancient 
or  modern,  wherever  they  appear. 

364.  But  the  elevations  at  which  we  have  found  such 
evidence  might  well  shake  belief  in  the  conclusions  to 
which  they  point.     Beside  the  Massa  Gorge,  at  1,000 
feet  above  the  present  Aletsch,  we  found  a  great  old 
moraine.  Descending  the  meadows  between  the  Bel  Alp 


146  THE  FORMS  OF  WATER  IN 

and  Flatten,  we  found  another,  now  clothed  with  grass, 
and  bearing  a  village  on  its  back.  But  I  wish  to  carry 
you  to  a  region  which  exhibits  these  evidences  on  a 
still  grander  and  more  impressive  scale.  We  have 
already  taken  a  brief  flight  to  the  valley  of  Hasli  and 
the  Glacier  of  the  Aar.  Let  us  make  that  glacier  our 
starting-point.  Walking  from  it  downwards  towards 
the  Griinsel,  we  pass  everywhere  over  rocks  singularly 
rounded,  and  fluted,  and  scarred.  These  appearances 
are  manifestly  the  work  of  the  glacier  in  recent  times. 
But  we  approach  the  Grimsel,  and  at  the  turning  of 
the  valley  stand  before  the  precipitous  granite  flank  of 
the  mountain.  The  traces  of  the  ancient  ice  are  here 
as  plain  as  they  are  amazing.  The  rocks  are  so  hard 
that  not  only  the  fluting  and  polishing,  but  even  the  fine 
scratches  which  date  back  unnamable  thousands  of 
years  are  as  evident  as  if  they  had  been  made  yester- 
day. We  may  trace  these  evidences  to  a  height  of  two 
thousand  feet  above  the  present  valley  bed.  It  is  in- 
dubitable that  an  ice-river  of  this  astounding  depth 
once  flowed  through  the  vale  of  Hasli. 

365.  Yonder  is  the  summit  of  the  Siedelhorn ;  and 
if  we  gain  it,  the  Unteraar  glacier  will  lie  like  a  map 
below  us.  From  this  commanding  point  we  plainly  see 
marked  upon  the  mountain  sides  the  height  to  which 
the  ancient  ice  extended.  The  ice-ground  part  of  the 
mountains  is  clearly  distinguished  from  the  splintered 
crests  which  in  those  distant  days  rose  above  the  surface 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.          147 

of  the  glacier,  and  which  must  have  then  appeared  as 
island  peaks  and  crests  in  the  midst  of  an  ocean  of  ice. 

366.  We  now  scamper  down  the  Siedelhorn,  get  once 
more  into  the  valley  of  Hasli,  along  which  we  follow 
for  more  than  twenty  miles  the  traces  of  the  ice.  Fluted 
precipices,  polished  slabs,  and  beautifully -rounded 
granite  domes.  Eight  and  left  upon  the  mountain 
flanks,  at  great  elevations,  the  evidences  appear.  We 
follow  the  footsteps  of  the  glacier  to  the  Lake  of 
Brientz  ;  and  if  we  prolonged  our  enquiries,  we  should 
learn  that  all  the  lake  beds  of  this  region,  at  the  time 
now  referred  to,  bore  the  burden  of  immense  masses 
of  ice. 

867.  Instead  of  the  vale  of  Hasli,  we  might  take  the 
valley  of  the  Rhone.  The  traces  of  a  mighty  glacier, 
which  formerly  filled  it,  may  be  followed  all  the  way  to 
Martigny,  which  is  60  miles  distant  from  the  present 
ice.  At  Martigny  the  Rhone  glacier  was  reinforced  by 
another  from  Mont  Blanc,  and  the  welded  masses 
moved  onward,  planing  the  mountains  right  and  left,  to 
the  Lake  of  Geneva,  the  basin  of  which  they  entirely 
filled.  Other  evidences  prove  that  the  glacier  did  not 
end  here,  but  pushed  across  the  low  country  until  it 
encountered  the  limestone  barrier  of  the  Jura  Moun- 
tains. 

§  54.  Erratic  Blocks. 

368.  What  are  these  other  evidences  ?  We  have 
seen  mighty  rocks  poised  on  the  moraines  of  the  Mer 


148  THE  FORMS  OF  WATER  IN 

de  Glace,  and  we  now  know  that,  unless  they  are  split 
and  shattered  by  the  frost,  these  rocks  will,  at  some 
distant  day,  be  landed  bodily  by  the  Glacier  des  Bois 
in  the  valley  of  Chamouni.  You  have  already  learned 
that  these  boulders  often  reveal  the  mineralogical  nature 
of  the  mountains  among  which  the  glacier  has  passed ; 
that  specimens  are  thus  brought  down  of  a  character 
totally  different  from  the  rocks  among  which  they  are 
finally  landed;  this  is  strikingly  the  case  with  the 
erratic  blocks  stranded  along  the  Jura. 

369.  For  the  Jura  itself,  as  already  stated,  is  lime- 
stone ;  there  is  no  trace  of  native  granite  to  be  found 
amongst   these  hills.     Still   along  the   breast   of  the 
mountain  above  the  town  of  Neufchatel,  and  at  about 
800  feet  above  the  lake  of  Neufchatel,  we  find  stranded 
a  belt  of  granite  boulders  from  Mont  Blanc.     And  when 
we  clear  the  soil  away  from  the  adjacent  mountain  side, 
we  find  upon  the  limestone  rocks  the  scarrings  of  the 
ancient  glacier  which  brought  the  boulders  here. 

370.  The  most  famous   of   these   rocks,  called  the 
Pierre  a  Bot,  measures  50  feet  in  length,  40  in  height, 
and   20   in  width.     Multiplying  these  three  numbers 
together,  we  obtain  40,000  cubic  feet  as  the  volume  of 
the  boulder. 

371.  But  this   is   small  compared  to   some   of  the 
rocks   which   constitute    the   freight    of   even  recent 
glaciers.     Let   us   visit   another   of  them.     We   have 
already  been  to  Stalden,  where  the  valley  divides  into 


CLOUDS  AND  KIVEES,  ICE  AND  GLACIERS.          149 

two  branches,  the  right  branch  running  to  St.  Nicholas 
and  Zermatt,  and  the  left  one  to  Saas  and  the  Monte 
Moro.  Three  hours  above  Saas  we  come  upon  the  end 
of  the  Allelein  glacier,  not  filling  the  main  valley,  but 
thrown  athwart  it  so  as  to  stop  its  drainage  like  a  dam. 
Above  this  ice-dam  we  have  the  Mattrnark  Lake,  and 
at  the  head  of  the  lake  a  small  inn  well  known  to 
travellers  over  the  Monte  Moro. 

372.  Close  to  this  inn  is  the  greatest  boulder  that 
we  have  ever   seen.     It  measures  240,000  cubic  feet. 
Looking  across  the  valley  we  notice  a  glacier  with  its 
present  end  half  a  mile  from  the  boulder.     The  stone, 
I  believe,  is   serpentine,  and  were   you   and  I  to  ex- 
plore the  Schwartzberg  glacier  to  its  upper  fastnesses, 
we    should  find  among  them   the   birthplace   of  this 
gigantic  stone.    Four-and-forty  years  ago,  when    the 
glacier  reached  the  place  now  occupied  by  the  boulder, 
it  landed  there  its  mighty  freight,  and  then  retreated. 
There  is  a  second  ice-borne  rock  at  hand  which  would  be 
considered  vast  were  it  not  dwarfed  by  the  aspect  of  its 
huger  neighbour. 

373.  Evidence  of  this  kind  might  be  multiplied  to  any 
extent.     In  fact,  at  this  moment,  distinguished  men, 
like  Professor  Favre  of  Geneva,  are  determining  from 
the  distribution  of  the  erratic  blocks  the  extent  of  the 
ancient  glaciers  of  Switzerland.     It  was,  however,  an 
engineer  named  Venetz  that  first  brought  these  evidences 
to  light,  and  announced  to  an  incredulous   world  the 


150  THE  FORMS  OF  WATER  IN 

vast  extension  of  the  ancient  ice.  M.  Agassiz  after- 
wards developed  and  wonderfully  expanded  the  dis- 
covery. Perhaps  the  most  interesting  observation 
regarding  ancient  glaciers  is  that  of  Dr.  Hooker, 
who,  during  a  recent  visit  to  Palestine,  found  the 
celebrated  Cedars  of  Lebanon  growing  upon  ancient 
moraines. 

§  55.  Ancient  Glaciers  of  England,  Ireland,  Scotland, 
and  Wales. 

374.  At  the  time  the  ice  attained  this  extraordinary 
development  in  the  Alps,  many  other  portions  of  Europe, 
where  no  glaciers  now  exist,  were  covered  with  them. 
In  the  Highlands  of  Scotland,  among  the  mountains  of 
England,  Ireland,  and  Wales,  the  ancient  glaciers  have 
written  their  story  as  plainly  as  in  the  Alps  themselves. 
I  should  like  to  wander  with  you  through  Borrodale  in 
Cumberland,  or  through  the  valleys  near  Bethgellert  in 
Wales.     Under  all  the  beauty  of  the  present  scenery  we 
should  discover  the  memorials  of  a  time  when  the  whole 
region  was  locked  in  the  embrace  of  ice.     Professor 
Ramsay  is  especially  distinguished  by  his  writings  on 
the  ancient  glaciers  of  Wales. 

375.  We  have  made  the  acquaintance  of  the  Reeks 
of  Magillicuddy  as   the    great  condensers  of  Atlantic 
vapour.     At  the  time  now  referred  to,  this  moisture 
did  not  fall  as  soft  and  fructifying  rain,  but  as  snow, 
which  formed  the  nutriment  of  great  glaciers.     A  chain 


CLOUDS  AND  EIVEKS,  ICE  AND  GLACISES.         151 

of  lakes  now  constitutes  the  chief  attraction  of  Killarney, 
the  Lower,  the  Middle,  and  the  Upper  Lake.  Let  us 
suppose  ourselves  rowing  towards  the  head  of  the  Upper 
Lake  with  the  Purple  Mountain  to  our  left.  Remem- 
bering our  travels  in  the  Alps,  you  would  infallibly  call 
my  attention  to  the  planing  of  the  rocks,  and  declare 
the  action  to  be  unmistakably  that  of  glaciers.  With 
our  attention  thus  sharpened,  we  land  at  the  head  of 
the  lake,  and  walk  up  the  Black  Valley  to  the  base  of 
Magillicuddy's  Eeeks.  Your  conclusion  would  be,  that 
this  valley  tells  a  tale  as  wonderful  as  that  of  Hasli. 

376.  We  reach  our  boat  and  row  homewards  along  the 
Upper  Lake.  Its  islands  now  possess  a  new  interest 
for  us.  Some  of  them  are  bare,  others  are  covered 
wholly  or  in  part  with  luxuriant  vegetation ;  but  both  the 
naked  and  clothed  islands  are  glaciated.  The  weather- 
ing of  ages  has  not  altered  their  forms  :  there  are  the 
Cannon  Rock,  the  Giant's  Coffin,  the  Man  of  War,  all 
sculptured  as  if  the  chisel  had  passed  over  them  in  our 
own  lifetime.  These  lakes,  now  fringed  with  tender 
woodland  beauty,  were  all  occupied  by  the  ancient  ice. 
It  has  disappeared,  and  seeds  from  other  regions  have 
been  wafted  thither  to  sow  the  trees,  the  shrubs,  the 
ferns,  and  the  grasses  which  now  beautify  Killarney. 
Man  himself,  they  say,  has  made  his  appearance  in  the 
world  since  that  time  of  ice  ;  but  of  the  real  period  and 
manner  of  man's  introduction  little  is  professed  to  be 
known  since,  to  make  them  square  with  science,  new 
8 


152  THE  FOKMS   OF  WATER  IN 

meanings  have  been  found  for  the  beautiful  myths  and 
stories  of  the  Bible. 

377.  It  is  the  nature  and  tendency  of  the  human 
mind  to  look  backward  and  forward ;  to  endeavour  to 
restore  the  past  and  predict  the  future.     Thus  endowed, 
from  data  patiently  and  painfully  won,  we  recover  in 
idea  a  state  of  things  which  existed  thousands,  it  may 
be  millions,  of  years  before  the  history  of  the  human' 
race  began. 

§  56.   The  Glacial  Epoch. 

378.  This  period  of  ice-extension  has  been  named  the 
Glacial  Epoch.     In  accounting  for  it  great  minds  have 
fallen  into  grave  errors,  as  we  shall  presently  see. 

379.  The  substance  on  which  we  have  thus  far  been 
working  exists  in  three  different  states :  as  a  solid  in 
ice ;  as    a  liquid  in  water ;  as  a  gas   in  vapour.     To 
cause  it  to  pass  from  one  of  these  states  to  the  next 
following  one,  heat  is  necessary. 

380.  Dig  a  hole  in  the  ice  of  the  Mer  de  Glace  in 
summer,  and  place  a  thermometer  in  the  hole ;  it  will 
stand  at  32°  Fahr.     Dip  your  thermometer  into  one  of 
the  glacier  streams ;  it  will  still  mark  32°.    The  water  is 
therefore  as  cold  as  ice. 

381.  Hence  the  whole  of  the  heat  poured  by  the  sun 
upon  the  glacier,  and  which  has  been  absorbed  by  the 
glacier,  is  expended  in  simply  liquefying  the  ice,  and 
not  in  rendering  either  ice  or  water  a  single  degree 
warmer. 


CLOUDS  AND  EIVEES,  ICE  AND  GLACIERS.          153 

382.  Expose  water  to  a  fire;  it  becomes  hotter  for  a 
time.     It  boils,  and  from  that  moment  it  ceases  to  get 
hotter.     After  it  has  begun  to  boil,  all  the  heat  com- 
municated by  the  fire  is  carried  away  by  the  steam, 
though  the  steam  itself  is  not  the  least  fraction  of  a  degree 
hotter  than  the  water. 

383.  In  fact,  simply  to  liquefy  ice  a  large  quantity  of 
heat  is  necessary,  and  to  vaporize  water  a  still  larger 
quantity  is  necessary.     And  inasmuch  as  this  heat  does 
not   render  the  water  warmer  than  the   ice,  nor  the 
steam  warmer  than  the  water,  it  was  at  one  time  sup- 
posed to  be  hidden  in  the  water   and  in  the  steam. 
And  it  was  therefore  called  latent  heat. 

384.  Let  us  ask  how  much  heat  must  the  sun  expend 
in  order  to  convert  a  pound  weight  of  the  tropical  ocean 
into  vapour  ?     This  problem  has  been  accurately  solved 
by  experiment.      It  would  require  in  round   numbers 
1,000  times  the  amount  of  heat  necessary  to  raise  one 
pound  of  water  one  degree  in  temperature. 

385.  But  the  quantity  of  heat  which  would  raise  the 
temperature  of  a  pound  of  water  one  degree  would  raise 
the  temperature  of  a  pound  of  iron  ten  degrees.     This 
has  been  also  proved  by  experiment.     Hence  to  convert 
one  pound  of  the  tropical  ocean  into  vapour  the  sun 
must  expend  10,000  times  as  much  heat  as  would  raise 
one  pound  of  iron  one  degree  in  temperature. 

386.  This  quantity  of  heat  would  raise  the.  tempera- 
ture of  5  Ibs.  of  iron  2,000  degrees,  which  is  the  fusing 
point  of  cast  iron  ;  at  this  temperature  the  metal  would 


154  THE  FOKMS  OF  WATER  IN 

nob  only  be  white  hot,  but  would  be  passing  into  the 
molten  condition. 

387.  Consider  the  conclusions  at  which  we  have  now 
arrived.     For  every  pound  of  tropical  vapour,  or  for 
every  pound  of  Alpine  ice  produced  by  the  congelation 
of  that  vapour,  an  amount  of  heat  has  been  expended 
by  the  sun  sufficient  to  raise  5  Ibs.  of  cast  iron  to  its 
melting-point. 

388.  It  would  not  be  difficult  to  calculate  approxi- 
mately the  weight  of  the  Mer  de  Glace  and  its  tribu- 
taries— to  say,  for  example,  that  they  contained  so  many 
millions  of  millions  of  tons  of  ice  and  snow.     Let  the 
place  of  the  ice  be  taken  by  a  mass  of  white-hot  iron  of 
quintuple  the  weight ;  with  such  a  picture  before  your 
mind  you  get  some  notion  of  the  enormous  amount  of 
heat  paid  out  by  the  sun  to  produce  the  present  glacier. 

389.  You  must  think  over  this,  until  it  is  as  clear  as 
sunshine.     For  you  must  never  henceforth  fall  into  the 
error  already  referred  to,  and  which  has  entangled  so 
many.     So  natural  was  the  association  of  ice  and  cold, 
that  even  celebrated  men  assumed  that  all  that  is  needed 
to  produce  a  great  extension  of  our  glaciers  is  a  dimi- 
nution  of   the   sun's  temperature.      Had  they    gone 
through  the  foregoing  reflections  and  calculations,  they 
would  probably  have  demanded  more  heat  instead  of  less 
for  the  production  of  a  'glacial  epoch.'     What  they 
really  needed  were  condensers  sufficiently  powerful  to 
congeal  the  vapour  generated  by  the  heat  of  the  sun. 


CLOUDS  AND  EIVERS,  ICE  AND  GLACIEES.         155 

§  57.  Glacier  Theories. 

390.  You  have  not  forgotten,  and  hardly  ever  can 
forget,  our  climbs  to  the  Cleft  Station.     Thoughts  were 
then  suggested  which  we  have  not  yet  discussed.     We 
saw  the  branch  glaciers  coming  down  from  their  neves, 
welding  themselves  together,  pushing  through  Trela- 
porte,   and   afterwards   moving  through  the    sinuous 
valley  of  the  Mer  de  Glace.     These  appearances  alone, 
without  taking  into  account  subsequent  observations, 
were  sufficient  to  suggest  the  idea  that  glacier  ice,  how- 
ever hard  and  brittle  it  may  appear,  is  really  a  viscous 
substance,  resembling   treacle,   or    honey,   or  tar,   or 
lava. 

§  58.  Dilatation  and  Sliding  Theories. 

391.  Still  this  was  not  the  notion  expressed  by  the 
majority   of   writers    upon    glaciers.      Scheuchzer   of 
Zurich,  a  great  naturalist,  visited  the  glaciers  in  1705, 
and  propounded  a  theory  of  their  motion.     Water,  he 
knew,  expands  in  freezing,  and  the  force  of  expansion  is 
so  great,  that  thick  bombshells  filled  with  water,  and 
permitted  to  freeze,  are,  as  we  know  (312),  shattered  to 
pieces  by  the  ice  within.    Scheuchzer  supposed  that  the 
water  in  the  fissures  of  the  glaciers,  freezing  there  and 
expanding  with  resistless  force,  was  the  power  which 
urged  the  glacier  downwards.     He  added  to  this  theory 
other  notions  of  a  less  scientific  kind. 


156  THE  FOKMS  OF  WATER  IN 

392.  Many  years  subsequently,  De  Charpentier  of  Bex 
renewed  and  developed  this  theory  with  such  ability 
and  completeness,  that  it  was  long  known  as  Charpen- 
tier's  Theory  of  Dilatation.      M.  Agassi z  for  a  time 
espoused  this  theory,  and  it  was  also  more  or  less  dis- 
tinctly held  by  other  writers.     The  glacier,  in  fact,  was 
considered  to  be  a  magazine  of  cold,  capable  of  freezing 
all   water  percolating   through   it.      The   theory  was 
abandoned  when  this  notion  of  glacier  cold  was  proved 
by  M.  Agassiz  to  be  untenable. 

393.  In  1760,  Altmann  and  Griiner  propounded  the 
view  that  glaciers  moved  by  sliding  over  their  beds. 
Nearly  forty  years  subsequently,  this  notion  was  revived 
by  De  Saussure,  and  it  has  therefore  been  called  '  De 
Saussure's  Theory,'  or  the  '  Sliding  Theory '  of  glacier 
motion. 

394.  There  was,  however,  but  little  reason  to  connect 
the  name  of  De  Saussure  with  this  or  any  other  theory 
of  glaciers.     Incessantly  occupied  in  observations   of 
another  kind,  this  celebrated  man  devoted  very  little 
time   or   thought  to   the  question  of  glacier  motion. 
What  he  has  written  upon  the  subject  reads  less  like 
the  elaboration  of  a  theory  than  the  expression  of  an 
opinion. 

§  59.  Plastic  Theory. 

395.  By  none  of  these  writers  is  the  property  of  vis- 
cosity or  plasticity  ascribed  to  glacier  ice ;  the  appear- 
ances of  many  glaciers  are,  however,  so  suggestive  of 


CLOUDS  AND  EIVERS,   ICE  AND  GLACIERS.          157 

tliis  idea  that  we  may  be  sure  it  would  have  found  more 
frequent  expression,  were  it  not  in  such  apparent  con- 
tradiction with  our  every-day  experience  of  ice. 

396.  Still  the  idea  found  its  advocates.     In  a  little 
book,   published   in  1773,   and   entitled   e  Picturesque 
Journey  to  the  Glaciers  of  Savoy,'  Bordier  of  Geneva 
wrote  thus  : — £  It  is  now  time  to  look  at  all  these  objects 
with  the  eyes  of  reason ;  to  study,  in  the  first  place,  the 
position  and  the  progression  of  glaciers,  and  to  seek  the 
solution  of  their  principal  phenomena.     At  the  first  as- 
pect of  the  ice-mountains  an  observation  presents  itself, 
which  appears  sufficient  to  explain  all.     It  is  that  the 
entire  mass  of  ice  is  connected  together,   and  presses 
from  above  downwards  after  the  manner  of  fluids.     Let 
us  then  regard  the  ice,  not  as  a  mass  entirely  rigid 
and  immobile,  but  as  a  heap  of  coagulated  matter,  or  as 
softened  wax,  flexible  and  ductile  to  a  certain  point.'  * 
Here  probably  for  the  first  time  the  quality  of  plasticity 
is  ascribed  to  the  ice  of  glaciers. 

397.  To  us,  familiar  with  the  aspect  of  the  glaciers, 
it  must  seem  strange  that  this  idea  once  expressed  did 
not  at  once  receive  recognition  and  development.     But 
in  those  early  days  explorers  were  few,  and  the  ( Pic- 
turesque Journey '  probably  but  little  known,  so  that 
the  notion  of  plasticity  lay  dormant  for  more  than  half 

*  I  am  indebted  to  my  distinguished  friend  Prof.  Studer  of  Berne  for 
directing  my  attention  to  Bordier's  book,  and  to  my  friends  at  the  British 
Museum  for  the  great  trouble  they  have  taken  to  find  it  for  me. 


158  THE  FOEMS  OF  WATEE  IN 

a  century.  But  Bordier  was  at  length  succeeded  by  a 
man  of  far  greater  scientific  grasp  and  insight  than 
himself.  This  was  Rendu,  a  Catholic  priest  and  canon 
when  he  wrote,  and  afterwards  Bishop  of  Annecy.  In 
1841  Eendu  laid  before  the  Royal  Academy  of  Sciences 
of  Savoy  his  '  Theory  of  the  Glaciers  of  Savoy,'  a  con- 
tribution for  ever  memorable  in  relation  to  this  subject.* 

398.  Rendu  seized  the  idea  of  glacier  plasticity  with 
great  power  and  clearness,  and  followed  it  resolutely  to 
its  consequences.     It  is  not  known  that  he  had  ever 
seen  the  work  of  Bordier;   probably  not,  as  he  never 
mentions  it.     Let  me  quote  for  you  some  of  Rendu's 
expressions,  which,  however,  fail  to  give  an  adequate 
idea  of  his  insight  and  precision  of  thought : — '  Between 
the  Mer  de  Glace  and  a  river  there  is  a  resemblance  so 
complete  that  it  is  impossible  to  find  in  the  glacier  a 
circumstance  which  does  not  exist  in  the  river.     In 
currents   of  water  the   motion   is  not  uniform  either 
throughout  their  width   or  throughout    their   depth. 
The  friction  of  the  bottom  and  of  the  sides,  with  the 
action  of  local  hindrances,  causes  the  motion  to  vary, 
and  only  towards   the   middle  of  the   surface  do  we 
obtain  the  full  motion.' 

399.  This  reads  like  a  prediction  of  what  has  since 
been   established  by   measurement.      Looking   at   the 
glacier  of  Mont  Dolent,  which  resembles  a  sheaf  in 
form,  wide  at  both  ends  and  narrow  in  the  middle,  and 

*  '  Memoirs  of  the  Academy/  vol.  x. 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.         159 

reflecting  that  the  upper  wide  part  had  become  narrow, 
and  the  narrow  middle  part  again  wide,  Rendu  observes, 
*  There  is  a  multitude  of  facts  which  seem  to  necessitate 
the  belief  that  glacier  ice  enjoys  a  kind  of  ductility 
which  enables  it  to  mould  itself  to  its  locality,  to  thin 
out,  to  swell,  and  to  contract  as  if  it  were  a  soft  paste.' 

400.  To  fully  test  his  conclusions,  Rendu  required 
the  accurate  measurement  of  glacier  motion.     Had  he 
added  to  his  other  endowments  the  practical  skill  of  a 
land-surveyor,  he  would  now  be  regarded  as  the  prince 
of  glacialists.     As  it  was  he  was  obliged  to  be  content 
with  imperfect  measurements.     In  one  of  his  excur- 
sions he  examined  the  guides  regarding  the  successive 
positions  of  a  vast  rock  which  he  found  upon  the  ice 
close  to  the  side  of  the  glacier.     The  mean  of  five  years 
gave  him  a  motion  for  this  block  of  40  feet  a  year. 

401.  Another  block,  the  transport  of  which  he  sub- 
sequently measured  more  accurately,  gave  him  a  velocity 
of  400  feet  a  year.     Note  his  explanation  of  this  dis- 
crepancy:— 'The  enormous  difference  of  these  two  obser- 
vations arises  from  the  fact  that  one  block  stood  near 
the  centre  of  the  glacier,  which  moves  most  rapidly, 
while  the  other  stood  near  the  side,  where  the  ice  is 
held  back  by  friction.'      So   clear  and  definite   were 
Rendu's  ideas  of  the  plastic  motion  of  glaciers,  that  had 
the  question  of  curvature  occurred  to  him,  I  entertain 
no  doubt  that  he  would  have  enunciated  beforehand  the 


160  THE  FOKMS  OF  WATER  IN 

shifting  of  the  point  of  maximum  motion  from  side  to 
side  across  the  axis  of  the  glacier  (§  25). 

402.  It  is  right  that  you  should  know  that  scientific 
men  do  not  always  agree  in  their  estimates  of  the  com- 
parative value  of  facts  and  ideas ;  and  it  is  especially 
right  that  you  should  know  that  your  present  tutor 
attaches  a  very  high  value  to  ideas  when  they  spring 
from  the  profound  and  persistent  pondering  of  superior 
minds,  and  are  not,  as  is  too  often  the  case,  thrown  out 
without  the  warrant  of  either  deep  thought  or  natural 
capacity.     It  is  because  I  believe  Rendu's  labours  fulfil 
this  condition,  that  I  ascribe  to  them  so  high  a  value. 
But  when  you  become  older  and  better  informed,  you 
may  differ  from  me ;  and  I  write  these  words  lest  you 
should  too  readily  accept  my  opinion  of  Kendu.     Judge 
me,  if  you  care   to   do  so,  when  your  knowledge  is 
matured.     I  certainly  shall  not  fear  your  verdict. 

403.  But,  much  as  I  prize  the  prompting  idea,  and 
thoroughly  as  I  believe  that  often  in  it  the  force  of 
genius  mainly  lies,  it  would,  in  my  opinion,  be  an  error 
of  omission  of  the  gravest  kind,  and  which,  if  habitual, 
would  ensure  the  ultimate  decay  of  natural  knowledge, 
to  neglect  verifying  our  ideas,  and  giving  them  outward 
reality  and  substance  when  the  means  of  doing  so  are 
at  hand.     In  science  thought,  as  far  as  possible,  ought 
to  be  wedded  to  fact.     This  was  attempted  by  Eendu, 
and  in  great  part  accomplished  by  Agassiz  and  Forbes. 


CLOUDS  AKD  RIVERS,  ICE  AND  GLACIERS.          161 

§  60.   Viscous  Theory. 

404.  Here  indeed  the   merits    of  the   distinguished 
glacialist  last  named  rise  conspicuously  to  view.     From 
the  able  and  earnest  advocacy  of  Professor  Forbes,  the 
public  knowledge  of  this  doctrine  of  glacial  plasticity  is 
almost  wholly  derived.     He  gave  the  doctrine  a  more 
distinctive  form ;  he  first  applied  the  term  viscous  to 
glacier  ice,  and  sought  to  found  upon  precise  measure- 
ments a  *  Viscous  Theory'  of  glacier  motion. 

405.  I  am  here  obliged  to  state  facts  in  their  historic 
sequence.    Professor  Forbes  when  he  began  his  investi- 
gations was  acquainted  with  the  labours  of  Eendu.    In 
his   earliest  work  upon  the  Alps  he  refers   to  those 
labours  in  terms  of  flattering  recognition.     But  though 
as  a  matter  of  fact  Eendu's  ideas  were  there  to  prompt 
him,  ifc  would  be  too  much  to  say  that  he  needed  their 
inspiration.     Had  Eendu  not  preceded  him,  he  might 
none  the  less  have  grasped  the  idea  of  viscosity,  execut- 
ing his  measurements  and  applying  his  knowledge  to 
maintain  it.     Be  that  as  it  may,  the  appearance  of  Pro- 
fessor Forbes  on  the  Unteraar  glacier  in  1841,  and  on 
the  Mer  de  Glace  in  1842,  and  his  labours  then  and 
subsequently,  have  given  him  a  name  not  to  be  for- 
gotten in  the  scientific  history  of  glaciers. 

406.  The  theory  advocated  by  Professor  Forbes  was 
enunciated  by  himself  in  these  words  : — '  A  glacier  is  an 
imperfect  fluid,  or  viscous  body,  wjiich  is  urged  down 


162  THE  FORMS  OF  WATER  IN 

slopes  of  certain  inclination  by  the  natural  pressure 
of  its  parts.'  In  1773  Bordier  wrote  thns : — '-As  the 
glaciers  always  advance  upon  the  plain,  and  never  dis- 
appear, it  is  absolutely  essential  that  new  ice  shall  per- 
petually take  the  place  of  that  which  is  melted :  it 
must  therefore  be  pressed  forward  from  above.  One 
can  hardly  refuse  then  to  accept  the  astonishing  truth, 
that  this  vast  extent  of  hard  and  solid  ice  moves  as 
a  single  piece  downwards.'  In  the  passage  already 
quoted  he  speaks  of  the  ice  being  pressed  as  a  fluid 
from  above.  These  constitute,  I  believe,  Bordier's  con- 
tributions to  this  subject.  The  quotations  show  his 
sagacity  at  an  early  date ;  but,  in  point  of  completeness, 
his  views  are  not  to  be  compared  with  those  of  Eendu 
and  Forbes. 

407.  I  must  not  omit  to  state  here  that  though  the 
idea  of  viscosity  has  not  been  espoused  by  M.  Agassiz, 
his  measurements,  and  maps  of  measurements,  on  the 
Unteraar  glacier  have  been  recently  cited  as  the  most 
clear  and  conclusive  illustrations  of  a  quality  which,  at 
all  events,  closely  resembles  vicosity. 

408.  But  why,  with  proofs  before  him  more  copious 
and  characteristic  than  those  of  any  other  observer,  does 
M.  Agassiz  hesitate  to  accept  the  idea  of  viscosity  as 
applied  to   ice?     Doubtless   because  he  believes  the 
notion  to  be  contradicted  by  our  every-day  experience 
of  the  substance. 

409.  Take  a  mass  of  ice  ten  or  even  fifteen  cubic  feet 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.         163 

|| 

in  volume ;  draw  a  saw  across  it  to  a  depth,  of  half  an 
inch  or  an  inch;  and  strike  a  pointed  pricker,  not 
thicker  than  a  very  small  round  file,  into  the  groove  ; 
the  substance  will  split  from  top  to  bottom  with  a  clean 
crystalline  fracture.  How  is  this  brittleness  to  be 
reconciled  with  the  notion  of  viscosity  ? 

410.  We  have,  moreover,  been  upon  the  glacier  and 
have  witnessed  the  birth  of  crevasses.     We  have  seen 
them  beginning  as  narrow  cracks  suddenly  formed,  days 
being  required  to  open  them  a  single  inch.     In  many 
glaciers  fissures  may  be  traced  narrow  and  profound  for 
hundreds  of  yards  through  the  ice.     What  does  this 
prove  ?     Did  the  ice  possess  even  a  very  small  modicum 
of  that  power  of  stretching,  which  is  characteristic  of  a 
viscous  substance,  such  crevasses  could  not  be  formed. 

411.  Still  it  is  undoubted  that  the  glacier  moves  like 
a  viscous  body.     The  centre  flows  past  the  sides,  the  top 
flows  over  the  bottom,  and  the  motion  through  a  curved 
valley  corresponds  to  fluid  motion.     Mr.  Mathews,  Mr. 
Froude,  and  above  all  Signor  Bianconi,  have,  more- 
over, recently  made  experiments  on  ice  which  strikingly 
illustrate  the  flexibility  of  the  substance.     These  experi- 
ments merit,  and  will  doubtless  receive,  full  attention 
at  a  future  time. 

§  61.  Reg  elation  Theory. 

412.  I  will  now  describe  to  you  an  attempt  that  has 
been  made  of  late  years  to  reconcile  the  brittleness  of 


164  THE  FORMS  OE  WATER  IN 

ice  with  its  motion  in  glaciers.  It  is  founded  on  the 
observation,  made  bj  Mr.  Faraday  in  1850,  that  when 
two  pieces  of  thawing-  ice  are  placed  together  they 
freeze  together  at  the  place  of  contact. 

413.  This  fact  may  not  surprise  you  ;  still  it  surprised 
Mr.  Faraday  and  others,  and  men  of  very  great  distinc- 
tion in  science  have  differed  in  their  interpretation  of  the 
fact.     The  difficulty  is  to  explain  where,  or  how,  in  ice 
already  thawing  the  cold  is  to  be  found  requisite  to  freeze 
the  film  of  water  between  the  two  touching  surfaces. 

41 4.  The  word  Regelation  was  proposed  by  Dr.  Hooker 
to  express  the  freezing  together  of  two  pieces  of  thawing 
ice  observed  by  Faraday ;  and  the  memoir  in  which  the 
term  was  first  used  was  published  by  Mr.  Huxley  and 
Mr.  Tyndall  in  the  Philosophical  Transactions  for  1857. 

415.  The/ac£  of  regelation,  and  its  application  irre- 
spective of  the  cause  of  regelation,  may  be  thus  illus- 
trated : — Saw  two  slabs  from  a  block  of  ice,  and  bring 
their  flat  surfaces  into  contact ;  they  immediately  freeze 
together.     Two  plates  of  ice,  laid  one  upon  the  other, 
with  flannel  round  them  overnight,  are  sometimes  so 
firmly  frozen  in  the  morning  that  they  will  rather  break 
elsewhere  than  along  their  surface  of  junction.     If  you 
enter  one  of  the  dripping  ice-caves  of  Switzerland,  you 
have  only  to  press  for  a  moment  a  slab  of  ice  against 
the  roof  of  the  cave  to  cause  it  to  freeze  there  and 
stick  to  the  roof. 

416.  Place  a  number  of  fragments  of  ice  in  a  basin  of 


CLOUDS  AND  EIVEKS,  ICE  AND   GLACIERS.         165 

water,  and  cause  them  to  touch  each  other ;  they  freeze 
together  where  they  touch.  You  can  form  a  chain  of 
such  fragments ;  and  then,  by  taking  hold  of  one  end 
of  the  chain,  you  can  draw  the  whole  series  after  it. 
Chains  of  icebergs  are  sometimes  formed  in  this  way 
in  the  Arctic  seas. 

417.  Consider  what  follows  from  these  observations. 
Snow  consists  of  small  particles   of  ice.     Now  if  by 
pressure  we  squeeze  out  the  air  entangled  in  thawing 
snow,  and  bring  the  little  ice-granules  into  close  contact, 
they  may  be  expected  to  freeze  together ;  and  if  the 
expulsion  of  the  air  be  complete,  the  squeezed  snow  may 
be  expected  to  assume  the  appearance  of  compact  ice. 

418.  We  arrive  at  this  conclusion  by  reasoning;  let 
us  now  test  it  by  experiment,  employing  a  suitable  hy- 
draulic press,  and  a  mould  to  hold  the  snow.     In  exact 
accordance  with  our  expectation,  we  convert  by  pressure 
the  snow  into  ice.* 

419.  Place  a  compact  mass  of  ice  in  a  proper  mould, 
and  subject  it  to  pressure.    It  breaks  in  pieces :  squeeze 
the  pieces  forcibly  together;  they  re-unite  by  regela- 
tion,  and  a  compact  piece  of  ice,  totally  different  in 
shape  from  the  first  one,  is  taken  from  the  press.     To 
produce  this  effect  the  ice  must  be  in  a  thawing  con- 
dition.     When   its   temperature   is   much    below  the 
melting   point  it  is  crushed  by  pressure,  not   into  a 

*  A  similar  experiment  was  made  by  the  Messrs.  Schlagintweit  prior  to 
the  discovery  which  explains  it,  and  which  therefore  remained  unsolved. 


166  THE  FOKMS  OP  WATER  IN 

pellucid  mass   of   another    shape,  but    into   a  white 
powder. 

420.  By  means  of  suitable  moulds  you  may  in  this 
way  change  the  shape  of  ice  to  any  extent,  turning  out 
spheres,  and  cups,  and  rings,  and  twisted  ropes  of  the 
substance;  the   change   of  form  in  these  cases  being 
effected  through  rude  fracture  and  regelation. 

421.  By  applying  the  pressure  carefully,  rude  fracture 
may  be  avoided,  and  the  ice  compelled  slowly  to  change 
its  form  as  if  it  were  a  plastic  body. 

422.  Now  our  first  experiment  illustrates  the  con- 
solidation of  the  snows  of  the  higher  Alpine  regions. 
The  deeper  layers  of  the  neve  have  to  bear  the  weight 
of  all  above  them,  and  are  thereby  converted  into  more 
or  less  perfect  ice.     And  our  last  experiment  illustrates 
the  changes  of  form  observed  upon  the  glacier,  where, 
by  the  slow  and  constant  application  of  pressure,  the  ice 
gradually  moulds  itself  to  the  valley,  which  it  fills. 

423.  In  glaciers,  however,  we  have  also  ample  illus- 
trations of  rude  fracture  and  regelation.     The  opening 
and  closing  of  crevasses  illustrate  this.     The  glacier 
is  broken  on  the  cascades  and  mended  at  their  bases. 
When  two  branch  glaciers  lay  their  sides  together,  the 
regelation  is   so  firm  that  they  begin  immediately  to 
flow   in  the  trunk   glacier  as   a   single  stream.     The 
medial  moraine  gives  no  indication  by  its  slowness  of 
motion  that  it  is  derived  from  the  sluggish  ice  of  the 
sides  of  the  branch  glaciers. 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.         167 

424.  The  gist  of  the  Kegelation  Theory  is  that  the  ice 
of  glaciers  changes  its  form  and  preserves  its  continuity 
under  pressure  which  keeps  its  particles  together.     But 
when  subjected  to  tension,  sooner  than  stretch  it  breaks, 
and  behaves  no  longer  as  a  viscous  body. 

§  62.  Cause  of  Reg  elation. 

425.  Here  the  fact  of  regelation  is  applied  to  explain 
the  plasticity  of  glacier  ice,  no  attempt  being  made  to 
assign  the  cause  of  regelation  itself.     They  are  two  en- 
tirely distinct  questions.     But  a  little  time  will  be  well 
spent  in  looking  more  closely  into  the  cause  of  regelation. 
You  may  feel  some  surprise  that  eminent  men  should  de- 
vote their  attention  to  so  small  a  point,  but  we  must  not 
forget  that  in  nature  nothing  is  small.    Laws  and  prin- 
ciples interest  the  scientific  student  most,  and  these  may 
be  as  well  illustrated  by  small  things  as  by  large  ones. 

426.  The  question  of  regelation  immediately  connects 
itself  with  that  of  '  latent  heat,'  already  referred  to,  (383) 
but  which  we  must  now  subject  to  further  examination. 
To  melt  ice,  as  already  stated,  a  large  amount  of  heat 
is  necessary,  and  in  the  case  of  the  glaciers  this  heat  is 
furnished  by  the  sun.     Neither  the  ice  so  melted  nor 
the  water  which  results  from  its  liquefaction  can  fall 
below  32°  Fahrenheit.     The  freezing  point  of  water  and 
the  melting  point  of  ice  touch  each  other,  as  it  were, 
at   this   temperature.     A   hair's-breadth  lower   water 
freezes ;  a  hair's-breadth  higher  ice  melts. 


168  THE  FORMS  OF  WATER  IN 

427.  But  if  the  ice  could  be  caused  to  melt  without  this 
supply  of  solar  heat,  a  temperature  lower  than  that  of 
ordinary  thawing  ice  would  result.     When  gnow  and 
salt,  or  pounded  ice  and  salt,  are  mixed  together,  the 
salt  causes   the  ice   to  melt,  and  in   this  way  a  cold 
of  20  or  80  degrees  below  the  freezing  point  may  be 
produced.     Here,  in   fact,  the  ice   consumes   its   own 
warmth  in  the  work  of  liquefaction.     Such  a  mixture 
of  ice  and  salt  is  .called  '  a  freezing  mixture.' 

428.  And  if  by  any  other  means  ice  at  the  temperature 
of  32°  Fahrenheit  could  be  liquefied  without  access  of 
heat  from  without,  the  water  produced  would  be  colder 
than  the  ice.  Now  Professor  James  Thomson  has  proved 
that  ice  may  be  liquefied  by  mere  pressure,  and  his 
brother,  Sir  William   Thomson,  has  also  shown  that 
water  under  pressure  requires  a  lower  temperature  to 
freeze  it  than  when  the  pressure  is  removed.     Professor 
Mousson  subsequently  liquefied  large  masses  of  ice  by  a 
hydraulic  press  ;  and  by  a  beautiful  experiment  Professor 
Helmholtz  has  proved  that  water  in  a  vessel  from  which 
the  air  has  been  removed,  and  which  is  therefore  relieved 
from  the  pressure  of  the  atmosphere,  freezes  and  forms 
ice-crystals  when  surrounded  by  melting  ice.     All  these 
facts  are  summed   up  in  the  brief  statement  that  the 
freezing  point  of  water  is  lowered  by  pressure.* 

429.  For  our  own  instruction  we  may  produce  the 

*  Professor  James  Thomson  and  Professor  Clausius  proved  this  inde- 
pendently and  almost  contemporaneously. 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.         169 

liquefaction  of  ice  by  pressure  in  the  following  way : 
— You  remember  the  beautiful  flowers  obtained  when  a 
sunbeam  is  sent  through  lake  ice(§  11),  and  you  have 
not  forgotten  that  the  flowers  always  form  parallel  to 
the  surface  of  freezing.  Let  us  cut  a  prism,  or  small 
column  of  ice  with  the  planes  of  freezing  running  across 
it  at  right  angles;  we  place  that  prism  between  two 
slabs  of  wood,  and  bring  carefully  to  bear  upon  it  the 
squeezing  force  of  a  small  hydraulic  press. 

430.  It  is  well  to  converge  by  means  of  a  concave  mirror 
a  good  light  upon  the  ice,  and  to  view  it  through  a 
magnifying  lens.     You  already  see  the  result.     Hazy 
surfaces  are  formed  in  the  very  body  of  the  ice,  which 
gradually  expand  as  the  pressure  is  slowly  augmented. 
Here  and  there  you  notice  something  resembling  crys- 
tallisation; fern-shaped  figures  run  with  considerable 
rapidity  through  the  ice,  and  when  you  look  carefully  at 
their  points  and  edges  you  find  them  in  visible  motion. 
These  hazy  surfaces  are  spaces  of  liquefaction,  and  the 
motion  you  see  is  that  of  the  ice  falling  to  water  under 
the  pressure.     That  water  is  colder  than  the  ice  was 
before  the  pressure  was  applied,  and  if  the  pressure  be 
relieved,  not  only  does  the  liquefaction  cease,  but  the 
water  re-freezes.     The  cold  produced  by  its  liquefaction 
under  pressure  is  suflicient  to  re-congeal  it  when  the 
pressure  is  removed. 

431.  If   instead  of  diffusing  the  pressure  over  sur- 
faces of  considerable  extent,  we  concentrate  it  on  a 


170  THE  FORMS  OF  WATER  IN 

small  surface,  the  liquefaction  will  of  course  be  more 
rapid,  and  this  is  what  Mr.  Bottomley  has  recently  done 
in  an  experiment  of  singular  beauty  and  interest.  Let 
us  support  on  blocks  of  wood  the  two  ends  of  a  bar  of 
ice  10  inches  long,  4  inches  deep,  and  3  wide,  and  let  us 
loop  over  its  middle  a  copper  wire  one-twentieth,  or 
even  one-tenth,  of  an  inch  in  thickness.  Connecting 
the  two  ends  of  the  wire  together,  and  suspending 
from  it  a  weight  of  12  or  14  pounds,  the  whole  pressure 
of  this  weight  is  concentrated  on  the  ice  which  sup- 
ports the  wire.  What  is  the  consequence  ?  The  ice 
underneath  the  wire  liquefies ;  the  water  of  liquefaction 
escapes  round  the  wire,  but  the  moment  it  is  relieved 
from  the  pressure  it  freezes,  and  round  about  the  wire, 
even  before  it  has  entered  the  ice,  you  have  a  frozen 
casing.  The  wire  continues  to  sink  in  the  ice;  the 
water  incessantly  escapes,  freezing  as  it  does  so  behind 
the  wire.  In  half  an  hour  the  weight  falls ;  the  wire 
has  gone  clean  through  the  ice.  You  can  plainly  see 
where  it  has  passed,  but  the  two  severed  pieces  of  ice 
are  so  firmly  frozen  together  that  they  will  break  else- 
where as  soon  as  along  the  surface  of  regelation. 

432.  Another  beautiful  experiment  bearing  upon  this 
point  has  recently  been  made  by  M.  Boussingault.  He 
filled  a  hollow  steel  cylinder  with  water  and  chilled  it. 
In  passing  to  ice  water,  as  you  know,  expands  (§  45) ; 
in  fact,  room  for  expansion  is  a  necessary  condition  of 
solidification.  But  in  the  present  case  the  strong  steel 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.         171 

resisted  the  expansion,  the  water  in  consequence  re- 
maining liquid  at  a  temperature  of  more  than  30°  Fahr. 
below  the  ordinary  freezing  point.  A  bullet  within  the 
cylinder  rattled  about  at  this  temperature,  showing 
that  the  water  was  still  liquid.  On  opening  the  tap  the 
liquid,  relieved  of  the  pressure,  was  instantly  converted 
into  ice. 

433.  It  is  only  substances  which  expand  on  solidify- 
ing that  behave  in  this  manner.   The  metal  bismuth,  as 
we  know,  is  an  example  similar  to  water ;  while  lead, 
wax,  or  sulphur,  all  of  which  contract  on  solidifying, 
have  their  point  of  fusion  heightened  by  pressure. 

434.  And  now  you  are  prepared  to  understand  Pro- 
fessor James  Thomson's  theory  of  regelation.     When 
two  pieces  of  ice  are  pressed  together  liquefaction,  he 
contends,  results.      The  water  spreads  out  around  the 
points  of  pressure,  and  when  released  re-freezes,  thus 
forming  a  kind  of  cement  between  the  pieces  of  ice. 

§  63.  Faraday9 s  View  of  Regelation. 

435.  Faraday's  view  of  regelation  is  not  so  easily 
expressed,  still  I  will  try  to  give  you  some  notion  of  it, 
dealing  in  the  first  place  with  admitted  facts.     Water, 
even  in  open  vessels,  may  be  lowered  many  degrees  below 
its  freezing  temperature,  and  still  remain  liquid ;  it  may 
also  be  raised  to  a  temperature  far  higher  than  its  boiling 
point,  and  still  resist  boiling.     This  is  due  to  the  mutual 
cohesion  of  the  water  particles,  which  resists  the  change 


172  THE  FORMS  OF  WATER  IN 

of  the   liquid   either   into  the  solid  or  the  vaporous 
condition. 

436.  But  if  into  the  over-chilled  water  you  throw  a 
particle  of  ice,  the  cohesion  is  ruptured,  and  congelation 
immediately   sets   in.     And   if    into   the   superheated 
water  you  introduce  a  bubble  of  air  or  of  steam,  cohe- 
sion is   likewise  ruptured,  and  ebullition  immediately 
commences. 

437.  Faraday  concluded  that  in  the  interior  of  any 
body,  whether  solid  or  liquid,  where  every  particle  is 
grasped  so  to  speak  by  the  surrounding  particles,  and 
grasps  them  in  turn,  the  bond  of  cohesion  is  so  strong 
as  to  require  a  higher  temperature  to  change  the  state 
of  aggregation  than  is  necessary  at  the  surface.     At  the 
surface  of  a  piece  of  ice,  for  example,  the  molecules  are 
free  on  one  side  from  the  control  of  other  molecules ; 
and  they  therefore  yield  to  heat  more  readily  than  in 
the  interior.     The  bubble  of  air  or  steam  in  overheated 
water  also  frees  the  molecules  on  one  side  ;  hence  the 
ebullition   consequent   upon   its   introduction.      Prac- 
tically speaking,  then,  the  point  of  liquefaction  of  the 
interior  ice  is  higher  than  that  of  the  superficial  ice. 
Faraday  also  refers   to   the  special  solidifying   power 
which  bodies  exert  upon  their  own  molecules.     Cam- 
phor in  a  glass  bottle  fills  the  bottle  with  an  atmos- 
phere of  camphor.    In  such  an  atmosphere  large  crystals 
of  the  substance  may  grow  by  the  incessant  deposition 
of  camphor  molecules  upon  camphor,  at  a  temperature 


CLOUDS  AND  KIVERS,   ICE  AND  GLACIERS.         173 

too  high  to  permit  of  the  slightest  deposit  upon  the 
adjacent  glass.  A.  similar  remark  applies  to  sulphur, 
phosphorus,  and  the  metals  in  a  state  of  fusion.  They 
are  deposited  upon  solid  portions  of  their  own  substance 
at  temperatures  not  low  enough  to  cause  them,  to  soli- 
dify against  other  substances. 

438.  Water  furnishes  an   eminent   example   of  this 
special    solidifying    power.     It    may    be    cooled    ten 
degrees   and   more   below   its   freezing  point  without 
freezing.     But  this  is  not  possible  if  the  smallest  frag- 
ment of  ice  be  floating  in  the  water.     It  then  freezes 
accurately  at  32°  Fahr.,  depositing  itself,  however,  not 
upon  the  sides  of  the  containing  vessel,  but  upon  the  ice. 
Faraday  observed  in  a  freezing  apparatus  thin  crystals 
of  ice  growing  in  ice-cold  water  to  a  length  of  six, 
eight,  or  ten  inches,  at  a  temperature  incompetent  to 
produce  their  deposition  upon  the  sides  of  the  contain- 
ing vessel. 

439.  And  now  we  are  prepared  for  Faraday's  view  of 
regelation.     When  the  surfaces  of  two  pieces  of  ice, 
covered  with  a   film  of  the  water  of  liquefaction,  are 
brought  together,  the  covering  film  is  transferred  from 
the  surface  to  the  centre  of  the  ice,  where  the  point 
of  liquefaction,  as  before  shown,  is  higher  than  at  the 
surface.    The  special  solidifying  power  of  ice  upon  water 
is  now  brought  into  play  on  both  sides  of  the  film.     Under 
these  circumstances,  Faraday  held  that  the  film  would 
congeal,  and  freeze  the  two  surfaces  together. 


174  THE  FORMS  OF  WATER  IN 

440.  The  lowering  of  the  freezing  point  by  pressure 
amounts  to  no  more  than  one -seventieth  of  a  degree 
Fahrenheit  for  a  whole  atmosphere.     Considering  the 
infinitesimal  fraction  of  this  pressure  which  is  brought 
into  play  in  some  cases  of  regelation,  Faraday  thought  its 
effect  insensible.  He  suspended  pieces  of  ice,  and  brought 
them  into  contact  without  sensible  pressure,  still  they 
froze  together.     Professor   James  Thomson,  however, 
considered  that  even  the  capillary  attraction  exerted 
between  two  such  masses  .would  be  sufficient  to  produce 
regelation.     You  may  make  the  following  experiments, 
in  further  illustration  of  this  subject : — 

441.  Place  a  small  piece  of  ice  on  water,  and  press  it 
underneath  the  surface  by  a  second  piece.     The  sub- 
merged piece  may  be  so  small  as  to  render  the  pressure 
infinitesimal ;  still  it  will  freeze  to  the  under  surface  of 
the  superior  piece. 

442.  Place  two  pieces  of  ice  in  a  basin  of  warm  water, 
and  allow  them  to  come  together ;  they  freeze  together 
•when  they  touch.     The  parts  surrounding  the  place  of 
contact  melt  away,  but  the  pieces  continue  for  a  time 
united  by  a  narrow  bridge  of  ice.     The  bridge  finally 
melts,  and  the  pieces  for  a  moment  are  separated.     But 
capillary  attraction  immediately  draws  them  together, 
and  regelation   sets  in  once  more.     A  new  bridge  is 
formed,  which  in  its  turn  is  dissolved,  the  separated 
pieces  again  closing  up.     A  kind  of  pulsation  is  thus 
established  between  the  two  pieces  of  ice.    They  touch, 


CLOUDS  AND  KIVERS,  ICE  AND  GLACIERS.         175 

they  freeze,  a  bridge  is  formed  and  melted ;  and  thus 
the  rhythmic  action  continues  until  the  ice  disappears. 

443.  According     to     Professor     James     Thomson's 
theory,  pressure  is  necessary  to  liquefy  the  ice.     The 
heat  necessary  for  liquefaction  must  be  drawn  from  the 
ice  itself,  and  the   cold  water  must  escape  from  the 
pressure  to  be  re-frozen.     Now  in  the  foregoing  experi- 
ments the  cold  water,  instead  of  being  allowed  to  freeze, 
issues  into  the  warm  water,  still  the  floating  fragments 
regelate  in  a   moment.     The  touching  surfaces   may, 
moreover,  be  convex ;  they  may  be  reduced  practically 
to  points,  clasped  all  round  by  the  warm  water,  which 
indeed  -rapidly  dissolves  them  as  they  approach  each 
other ;  still  they  freeze  immediately  when  they  touch. 

444.  You   may  learn   from   this   discussion   that  in 
scientific  matters,  as  in  all  others,  there  is  room  for 
differences  of  opinion.     The  frame  of  mind  to  be  culti- 
vated here  is  a  suspension  of  judgment  as  long  as  the 
meaning  remains  in  doubt.     It  may  be  that  Faraday's 
action  and  Thomson's  action  come  both  into  play.     I 
cannot  do  better  than  finish  these  remarks  by  quoting 
Faraday's  own  concluding  words,  which  show  how  in 
his  mind  scientific  conviction  dwelt  apart  from  dogma- 
tism : — '  No  doubt,'   he   says,    '  nice   experiments  will 
enable  us  hereafter  to  criticise  such  results  as  these, 
and  separating  the  true  from  the  untrue  will  establish 
the  correct  theory  of  regelation.' 

9 


176  TEE  FORMS  OF  WATER  IN 

§  64.   The  Blue  Veins  of  Glaciers. 

445.  We    now   approach   the    end,   one    important 
question  only  remaining  to  be  discussed.     Hitherto  we 
have  kept  it  back,  for  a  wide  acquaintance   with  the 
glaciers  was  necessary  to  its  solution.     We  had  also 
to  make  ourselves  familiar  by  actual  experiment  with 
the  power  of  ice,  softened  by  thaw,  to  yield  to  pressure, 
and  to  liquefy  under  such  pressure. 

446.  Snow  is   white.      But  if  you  examine   its  in- 
dividual particles  you  would  call  them  transparent,  not 
white.     The  whiteness  arises  from  the  mixture  of  the 
ice  particles  with  small  spaces  of  air.     In  the  case  of 
all  transparent  bodies  whiteness  results  from  such   a 
mixture.     The  clearest  glass  or  crystal  when  crushed 
becomes  a  white  powder.     The  foam  of  champagne  is 
white  through  the  intimate  admixture  of  a  transparent 
liquid  with  transparent  carbonic  acid  gas.     The  whitest 
paper,  moreover,  is  composed  of  fibres  which  are   in- 
dividually transparent. 

447.  It  is  not,  however,  the  air  or  the  gas,  but  the 
optical  severance  of  the  particles,  giving  rise  to  a  mul- 
titude of  reflexions  of  the  white  solar  light  at  their 
surfaces,  that  produces  the  whiteness. 

448.  The  whiteness  of  the  surface  of  a  clean  glacier 
(112),  and  of  the  icebergs  of  the  Margelin  See  (357), 
has   been   already  referred  to   a  similar  cause.      The 
surface  is  broken  into  innumerable  fissures  by  the  solar 


CLOUDS  AND  EIVEES,   ICE  AND  GLACIERS.         177 

heat,  the  reflexion  of  solar  light  from  the  sides  of  the 
little  fissures  producing  the  observed  appearance. 

449.  In  like  manner  if  you  freeze  water  in  a  test- 
tube  by  plunging  it  into  a  freezing  mixture,  the  ice 
produced   is  white.      For  the  most  part  also  the  ice 
formed  in  freezing  machines  is  white.     Examine  such 
ice,  and  you  will  find  it  filled  with  small  air-bubbles. 
When  the  freezing  is  extremely  slow  the  crystallising 
force  pushes  the  air  effectually  aside,  and  the  result- 
ing ice  is  transparent ;  when  the  freezing  is  rapid,  the 
air  is  entangled  before  it  can  escape,  and  the  ice  is 
translucent.      But   even  in  the  case  of  quick  freezing 
Mr.  Faraday  obtained  transparent  ice  by  skilfully  re- 
moving the  air-bubbles  as  fast  as  they  appeared  with 
a  feather. 

450.  In  the  case  of  lake  ice  the  freezing  is  not  uni- 
form, but  intermittent.    It  is  sometimes  slow,  sometimes 
rapid.     When  slow  the  air  dissolved  in  the  water  is 
effectually  squeezed  out  and  forms  a  layer  of  bubbles  on 
the  under-surface  of  the  ice.     An  act  of  sudden  freezing 
entangles  this  air,  and  hence  we  find  lake  ice  usually 
composed  of  layers  alternately  clear,  and  filled  with 
bubbles.    Such  layers  render  it  easy  to  detect  the  planes 
of  freezing  in  lake  ice. 

451.  And  now  for  the  bearing  of  these  facts.     Under 
the  fall  of  the  Geant,  at  the  base  of  the  Talefre  cascade, 
ant!  lower  down  the  Mer  de  Glace ;  in  the  higher  re- 
gions of  the  Grindelwald,  the  Aar,  the  Aletsch  and  the 


178  THE  FOKMS  OF  WATER  IN 

Gorner  glaciers,  the  ice  does  not  possess  the  trans- 
parency which  it  exhibits  near  the  ends  of  the  glaciers. 
It  is  white,  or  whitish.  Why?  Examination  shows 
it  to  be  filled  with  small  air-bubbles  ;  and  these,  as  we 
now  learn,  are  the  cause  of  its  whiteness. 

452.  They  are  the  residue  of  the  air  originally  en- 
tangled in  the  snow,  and  connected,  as  before  stated, 
with  the  whiteness  of  the  snow.    During  the  descent  of 
the  glacier,  the  bubbles  are  gradually  expelled  by  the 
enormous  pressures  brought  to  bear  upon  the  ice.     Not 
only  is  the  expulsion  caused  by  the  mechanical  yielding 
of  the  soft  thawing  ice,  but  the  liquefaction  of  the  sub- 
stance at  places  of  violent  pressure,  opening,  as  it  does, 
fissures  for  the  escape  of  the  air,  must  play  an  import- 
ant part  in  the  consolidation  of  the  glacier. 

453.  The  expulsion  of  the  bubbles  is,  however,  not 
uniform;  for  neither  ice  nor  any  other  substance  offers 
an  absolutely  uniform  resistance  to  pressure.     At  the 
base  of  every  cascade  that  we  have  visited,  and  on  the 
walls  of  the  crevasses  there  formed,  we  have  noticed  in- 
numerable blue  streaks  drawn  through  the  white  trans- 
lucent ice,  and  giving  the  whole  mass  the  appearance 
of  lamination.     These  blue  veins  turned  out  upon  ex- 
amination to  be  spaces  from  which  the  air-bubbles  had 
been  almost  wholly  expelled,  translucency  being  thus 
converted  into  transparency. 

454.  This  is  the  veined  or  ribboned  structure  of  gla- 
ciers, regarding  the  origin  of  which  diverse  opinions  are 
now  entertained. 


CLOUDS  AND  KIVEKS,  ICE  AND  GLACIERS.  179 

455.  It  is  now  our  duty  to  take  up  the  problem,  and 
to  solve  it  if  we  can.     On  the  neves  of  the  Col  du 
Geant,  and  other  glaciers,  we  have  found  great  cracks, 
and  faults,  and  Bergschrunds,  exposing  deep  sections  of 
the  neve ;  and  on  these  sections  we  have  found  marked 
the  edges  of  half-consolidated  strata  evidently  produced 
by  successive  falls  of  snow.     The  neve  is  stratified  be- 
cause its  supply  of  material   from  the  atmosphere  is 
intermittent,  and  when  we  first  observed  the  blue  veins 
we  were  disposed  to  regard  them  as  due  to  this  stratifi- 
cation. 

456.  But  observation    and   reflexion  soon  dispelled 
this  notion.     Indeed  it  could  hardly  stand  in  the  pre- 
sence of  the  single  fact  that  at  the  bases  of  the  ice-falls 
the  veins  are  always  vertical,  or  nearly  so.     We  saw  no 
way  of  explaining  how  the  horizontal  strata  of  the  neve 
could  be  so  tilted  up  at  the  base  of  the  fall  as  to  be  set 
on  edge.     Nor  is  the  aspect  of  the  veins  that  of  stratifi- 
cation. 

457.  On  the  central  portions  of  the  cascades,  more- 
over, there  are  no  signs  of  the  veins.     At  the  bases 
they  first  appear,  reaching  in  each  case  their  maximum 
development  a  little  below  the  base.     As  you  and  I 
stood  upon  the  heights  above  the  Zasenberg  and  scru- 
tinised  the   cascade   of   the    otrahleck   branch  of  the 
Grindelwald  glacier,  we  could  not  doubt  that  the  base 
of  the  fall  was  the  birthplace  of  the  veins.     We  called 
this  portion  of  the  glacier  a ( Structure  Mill,'  intimating 


180 


THE  FOEMS  OF  WATER  IN 


that  here,  and  not  on  the  neve,  the  veined  structure 
was  manufactured. 


SECTION  OP  ICEFALL,  AND  GLACIER  BELOW  IT,   SHOWING:  ORIGIN  OF  VEINED 
STRUCTURE. 

458.  This,  however,  is,  at  bottom,  the  language  of 
strong  opinion  merely,  not  that  of  demonstration ;  and  in 
science  opinion  ought  to  content  us  only  so  long  as 
positive  proof  is  unattainable.     The  love  of  repose  must 
not  prevent  us  from  seeking  this  proof.    There  is  no 
sterner  conscience  than  the  scientific   conscience,  and 
it  demands,  in  every  possible  case,  the  substitution  for 
private  conviction  of  demonstration  which  shall  be  con- 
clusive to  all. 

459.  Let  us,  for  example,  be  shown  a  case  in  which 
the   stratification   of  the  neve  is  prolonged    into  the 
glacier ;  let  us  see  the  planes  of  bedding  and  the  planes 
of  lamination  existing  side  by  side,  and  still  indubitably 


CLOUDS  AND   RIVERS,  ICE  AND   GLACIERS. 


181 


distinct.  Such  an  observation  would  effectually  exclude 
stratification  from  the  problem  of  the  veined  structure, 
and  through  the  removal  of  this  tempting  source  of 
error,  we  should  be  rendered  more  free  to  pursue  the 
truth. 

460.  We  sought  for  this  conclusive  test  upon  the 
Mer  de  Glace,  but  did  not  find  it.  We  sought  it  on  the 
Grindelwald,  and  the  Aar  glaciers,*  with  an  equal  want 
of  success.  On  the  Aletsch  glacier,  for  the  first  time, 
we  observed  the  apparent  coexistence  of  bedding  and 
structure,  the  one  cutting  the  other  upon  the  walls  of 
the  same  crevasse.  Still  the  case  was  not  sufficiently  pro- 
nounced to  produce  entire  conviction,  and  we  visited  the 
Gorner  glacier  with  the  view  of  following  up  our  quest. 


STRUCTURE  AND  BEDDING  ON  ALETSCH  GLACIER. 

461.  Here  day  after  day  added  to  the  conviction  that 
the  bedding  and  the  structure  were  two  different  things. 

*  M.  Agassiz,  however,  reports  a  case  of  the  kind  upon  the  glacier  of  the 
Aar. 


182  THE  FORMS   OF  WATER.  IN 

Still  day  after  day  passed  without  revealing  to  us  the 
final  proof.  Surely  we  have  not  let  our  own  ease  stand 
in  the  way  of  its  attainment,  and  if  we  retire  baffled 
we  shall  do  so  with  the  consciousness  of  having  done 
our  best.  Yonder,  however,  at  the  base  of  the  Mat- 
terhorn,  is  the  Furgge  glacier  that  we  have  not  yet 
explored.  Upon  it  our  final  attempt  must  be  made. 

462.  We  get  upon  the  glacier  near  its  end,    and 
ascend  it.     We  are  soon  fronted  by  a  barrier  composed 
of  three  successive  walls  of  neve,  the  one  rising  above 
the  other,  and  each  retreating  behind  the  other.     The 
bottom  of  each  wall  is  separated  from  the  top  of  the 
succeeding  one  by  a  ledge,  on  which  threatening  masses 
of  broken  neve  now  rest.      We  stand  amid  blocks  and 
rubbish  which  have  been    evidently   discharged  from 
these  ledges,  on  which  other  masses,  ready  apparently  to 
tumble,  are  now  poised. 

463.  On  the  vertical  walls  of  this  barrier  we  see, 
marked  with  the  utmost  plainness,  the  horizontal  lines 
of  stratification,  while  something  exceedingly  like  the 
veined  structure  appears  to  cross  the  lines  of  bedding 
at  nearly  a  right  angle.     The  vertical  surface  is,  how- 
ever weathered,  and  the  lines  of  structure,  if  they  be 
such,  are  indistinct.    The  problem  now  is  to  remove  the 
surface,  and  expose  the  ice  underneath.     It  is  one  of 
the  many  cases  that  have  come  before  us,  where  the 
value  of  an  observation  is  to  be  balanced  against  the 
danger  which  it  involves. 


CLOUDS  AND  RIVERS,   ICE  AND   GLACIERS. 


183 


464.  We  do  nothing  rashly ;  but,  scanning  the  ledges 
and  selecting  a  point  of  attack,  we  conclude  that  the 
danger  is  not  too  great  to  be  incurred.  We  advance 
to  the  wall,  remove  the  surface,  and  are  rewarded  by 
the  discovery  underneath  it  of  the  true  blue  veins. 
They,  moreover,  are  vertical,  while  the  bedding  is  hori- 
zontal. Bruce,  as  you  know,  was  defeated  in  many  a 
battle,  but  he  persisted  and  won  at  last.  Here,  upon 
the  Furgge  glacier,  you  also  have  fought  and  won 
your  little  Bannockburn. 


STRUCTURE  AND  BEDDING  ON  FURGGE  GLACIER. 

465.  But  let  us  not  use  the  language  of  victory  too 
soon.     The  stratification  theory  has  been  removed  out 
of  the  field  of  explanation,  but  nothing  has  as  yet  been 
offered  in  its  place. 

§  65.  Relation  of  Structure  to  Pressure. 

466.  This  veined  structure  was  first  described  by  the 
distinguished  Swiss  naturalist,  Guyot,  now  a  resident  in 


184  THE  FOKMS  OF  WATER  IN 

the  United  States.  From  the  Grimsel  Pass  I  have 
already  pointed  out  to  you  the  Gries  glacier  over- 
spreading the  mountains  at  the  opposite  side  of  the 
valley  of  the  Rhone.  It  was  on  this  glacier  that 
M.  Guyot  made  his  observation. 

467.  CI  saw,'  he  said,  'under  my  feet  the  surface  of 
the  entire  glacier  covered  with  regular  furrows,  from 
one  to  two  inches  wide,  hollowed  out  in  a  half-snowy 
mass,  and  separated  by  protruding  plates  of  harder  and 
more  transparent  ice.     It  was  evident  that  the  glacier 
here  was  composed  of  two  kinds  of  ice,  one  that  of  the 
furrows,  snowy  and  more  easily  melted ;  the  other  of 
the  plates,  more  perfect,  crystalline,  glassy,  and  resis- 
tant ;  and  that  the  unequal  resistance  which  the  two 
kinds  of  ice  presented  to  the  atmosphere  was  the  cause 
of  the  ridges. 

468.  'After  having  followed  them  for  several  hun- 
dred yards,  I  reached  a  crevasse  twenty  or  thirty  feet 
wide,  which,  as  it  cut  the  plates  and  furrows  at  right 
angles,  exposed  the  interior  of  the  glacier  to  a  depth  of 
thirty  or  forty  feet,  and  gave  a  beautiful  transverse 
section  of  the  structure.     As  far  as  my  eyes  could  reach, 
I  saw  the  mass  of  the  glacier  composed  of  layers  of 
snowy  ice,  each  two  of  which  were  separated  by  one  of 
the   hard  plates  of  which  I  have  spoken,  the  whole 
forming  a  regularly  laminated  mass,  which  resembled 
certain  calcareous  slates.5 

469.  I  have  not  failed  to  point  out  to  you  upon  all 


CLOUDS  AND  EIVEKS,  ICE  AND  GLACIEES.          185 

the  glaciers  that  we  have  visited  the  little  superficial 
furrows  here  described;  and  you  have,  moreover, 
noticed  that  in  the  furrows  mainly  is  lodged  the  finer 
dirt  which  is  scattered  over  the  glacier.  They  sug- 
gest the  passage  of  a  rake  over  the  ice.  And  when- 
ever these  furrows  were  interrupted  by  a  crevasse,  the 
veined  structure  invariably  revealed  itself  upon  the 
walls  of  the  fissure.  The  surface  grooving  is  indeed 
an  infallible  indication  of  the  interior  lamination  of 
the  ice. 

470.  We   have  tracked   the   structure   through  the 
various  parts  of  the  glaciers  at  which  its  appearance 
was  most  distinct ;  and  we  have  paid  particular  atten- 
tion to  the  condition  of  the  ice  at  these  places.     The 
very  fact  of  its  cutting  the  crevasses  at  right  angles  is 
significant.     We  know  the  mechanical   origin  of  the 
crevasses ;  that  they  are  cracks  formed  at  right  angles 
to  lines  of  tension.     But  since  the  crevasses  are  also 
perpendicular  to  the  planes  of  structure,  these  planes 
must  be  parallel  to  the  lines  of  tension. 

471.  On  the  glaciers,  however,  tension  rarely  occurs 
alone.     At  the  sides  of  the  glacier,  for  example,  where 
marginal  crevasses  are  formed,  the  tension  is  always 
accompanied  by  pressure ;  the  one  force  acting  at  right 
angles   to    the    other.      Here,    therefore,   the   veined 
structure,  which  is  parallel  to  the  lines  of  tension,  is 
perpendicular  to  the  lines  of  pressure. 

472.  That  this  is  so  will  be  evident  to  you  in  a 


186  THE  FORMS  OF  WATER  IN 

moment.  Let  the  adjacent  figure  represent  the  channel 
of  the  glacier  moving  in  the  direction  of  the  arrow. 
Suppose  three  circles  to  be  marked  upon  the  ice,  one  at 
the  centre  and  the  two  others  at  the  sides.  In  a  glacier 


of  uniform  inclination  all  these  circles  would  move 
downward,  the  central  one  only  remaining  a  circle.  By 
the  retardation  of  the  sides  the  marginal  circles  would 
be  drawn  out  to  ovals.  The  two  circles  would  be  elon- 
gated in  one  direction,  and  compressed  in  another. 
Across  the  long  diameter,  which  is  the  direction  of 
strain,  we  have  the  marginal  crevasses ;  across  the  short 
diameter  m  n,  which  is  the  direction  of  pressure,  we  have 
the  marginal  veined  structure. 

473.  This  association  of  pressure  and  structure  is 
invariable.  At  the  bases  of  the  cascades,  where  the 
inclination  of  the  bed  of  the  glacier  suddenly  changes, 
the  pressure  in  many  cases  suffices  not  only  to  close  the 
crevasses  but  to  violently  squeeze  the  ice.  At  such 
places  the  structure  always  appears,  sweeping  quite 
across  the  glacier.  When  two  branch  glaciers  unite, 
their  mutual  thrust  intensifies  the  pre-existing  marginal 
structure  of  the  branches,  and  developes  new  planes  of 
lamination.  Under  the  medial  moraines,  therefore,  we 


CLOUDS  AND  RIVEES,  ICE  AND  GLACIERS.  187 

have  usually  a  good  development  of  the  structure.  It 
is  finely  displayed,  for  example,  under  the  great  medial 
moraine  of  the  glacier  of  the  Aar. 

474.  Upon  this  glacier,  indeed,  the  blue  veins  were 
observed  independently  three  years  after  M.  Guyot  had 
first  described  them.     I  say  independently,  because  M. 
Guyot's  description,  though  written  in  1838,  remained 
unprinted,  and  was  unknown  in  1841  to  the  observers  on 
the  Aar.     These  were  M.  Agassiz  and  Professor  Forbes. 
To  the  question  of  structure  Professor  Forbes  subse- 
quently  devoted  much  attention,  and  it   was   mainly 
his  observations  and  reasonings  that  gave  it  the  im- 
portant position  now  assigned  to  it  in  the  phenomena 
of  glaciers. 

475.  Thus  without  quitting  the  glaciers  themselves,  we 
establish  the  connexion  between  pressure  and  structure. 
Is  there  anything  in  our  previous  scientific  experience 
with  which  these  facts  may  be  connected  ?     The  new 
knowledge  of  nature  must  always  strike  its  roots  into 
the  old,  and  spring  from  it  as  an  organic  growth. 

§  66.  Slate  Cleavage  and  Glacier  Lamination. 

476.  M.   Guyot  threw  out  an  exceedingly  sagacious 
nint,  when  he  compared  the  veined   structure   to  the 
cleavage  of  slate  rocks.     We  must  learn  something  of 
this  cleavage,   for  it  really   furnishes  the  key  to  the 
problem  which  now  occupies  us.     Let  us  go  then  to  the 


188  THE  FOKMS  OF  WATEE  IN 

quarries  of  Bangor  or  Cumberland,  and  observe  the 
quarry  men  in  their  sheds  splitting  the  rocks.  With  a 
sharp  point  struck  skilfully  into  the  edge  of  the  slate, 
they  cause  it  to  divide  into  thin  plates,  fit  for  roofing 
or  ciphering,  as  the  case  may  be.  The  surfaces  along 
which  the  rock  cleaves  are  called  its  planes  of  cleavage. 

477.  All  through  the  quarry  you  notice  the  direction 
of  these  planes  to  be  perfectly  constant.     How  is  this 
laminated  structure  to  be  accounted  for  ? 

478.  You  might  be  disposed  to  consider  that  cleavage 
is  a  case  of  stratification  or  bedding ;  for  it  is  true  that 
in  various  parts  of  England  there  are  rocks  which  can 
be  cloven  into  thin  flags  along  the  planes  of  bedding. 
But  when  we  examine  these  slate  rocks  we  verify  the 
observation,  first  I  believe  made  by  the  eminent  and 
venerable  Professor  Sedgwick,  that  the  planes  of  bed- 
ding usually  run  across  the  planes  of  cleavage. 

479.  We  have  here,  as  you  observe,  a  case  exactly 
similar  to  that  of  glacier  lamination,  which  we  were 
at  first  disposed  to  regard  as  due  to  stratification.     We 
afterwards,  however,  found  planes  of  lamination  crossing 
the  layers  of  the  neve,  exactly  as  the  planes  of  cleavage 
cross  the  beds  of  slate  rocks. 

480.  But  the  analogy  extends  further.    Slate  cleavage 
continued  to  be  a  puzzle  to  geologists  till  the  late  Mr. 
Daniel  Sharpe  made  the  discovery  that  shells  and  other 
fossils    and  bodies  found  in  slate  rocks  are  invariably 
flattened  out  in  the  planes  of  cleavage. 


CLOUDS  AND  EIVEHS.  ICE  AND  GLACIERS.          189 

481.  Turn    into    any   well -arranged   museum — for 
example,  into  the  School  of  Mines  in  Jermyn  Street,  and 
observe  the  evidence  there  collected.     Look  particularly 
to  the  fossil  trilobites  taken  from  the  slate  rock.     They 
are  in  some  cases  squeezed  to  one  third  of  their  primi- 
tive  thickness.     Numerous  other   specimens    show   in 
the  most  striking  manner  the  flattening  out  of  shells. 

482.  To  the  evidence  adduced  by  Mr.    Sharpe,  Mr. 
Sorby  added  other  powerful  evidence,  founded  upon  the 
microscopic  examination  of  slate  rock.     Taking  both 
into  account,  the  conclusion  is   irresistible  that   such 
rocks  have  suffered  enormous  pressure  at  right  angles 
to  the  planes  of  cleavage,  exactly  as  the  glacier  has 
demonstrably  suffered  great  pressure  at  right  angles  to 
its  planes  of  lamination, 

483.  The  association  of  pressure  and  cleavage  is  thus 
demonstrated ;  but  the  question  arises,  do  they  stand  to 
each  other  in  the  relation  of  cause  and  effect?     The 
only  way  of  replying  to   this  question  is  to  combine 
artificially  the  conditions  of  nature,  and  see  whether 
we  cannot  produce  her  results. 

484.  The  substance  of  slate  rocks  was  once  a  plastic 
mud,  in  which  fossils  were  embedded.     Let  us  imitate 
the  action  of  pressure  upon  such  mud  by  employing, 
instead  of  it,  softened  white  wax.     Placing  a  ball  of  the 
wax  between  two  glass  plates,  wetted  to  prevent  it  from 
sticking,  we  apply  pressure  and  flatten  out  the  wax. 

485.  The  flattened  mass  is  at  first  too  soft  to  cleave 


190  THE  FOEMS  OF  WATER  IN 

sharply ;  but  you  can  see,  by  tearing,  that  it  is  lami- 
nated. Let  us  chill  it  with  ice.  We  find  afterwards 
that  no  slate  rock  ever  exhibited  so  fine  a  cleavage. 
The  laminae,  it  need  hardly  be  said,  are  perpendicular 
to  the  pressure. 

486.  One  cause  of  this  lamination  is  that  the  wax  is 
an  aggregate  of  granules  the  surfaces  of  which  are  places 
of  weak  cohesion ;    and   that   by   the   pressure   these 
granules   are  squeezed  flat,  thus   producing  planes   of 
weakness  at  right  angles  to  the  pressure. 

487.  But  the  main  cause  of  the  cleavage  1  take  to  be 
the  lateral  sliding  of  the  particles  of  wax  over  each 
other.     Old   attachments   are   thereby   severed,  which 
the  new  ones  fail  to  make  good.     Thus  the  tangential 
sliding  produces  lamination,  as  the  rails  near  a  station 
are  caused  to  exfoliate  by  the  gliding  of  the  wheel. 

488.  Instead   of  wax  we  may  take  the  slate  itself, 
grind  it  to  fine  powder,  add  water,  and  thus  reproduce 
the  pristine  mud.     By  the  proper  compression  of  such 
mud,  in  one  direction,  the  cleavage  is  restored. 

489.  Call  now  to  mind  the  evidences  we  have  had 
of  the   power    of   thawing   ice   to   yield  to   pressure. 
Recollect  the  shortening  of  the  Glacier  du  Geant,  and 
the  squeezing  of  the  Glacier  de  Lechaud,  at  Trelaporte. 
Such  a  substance,  slowly  acted*  upon  by  pressure,  will 
yield  laterally.     Its  particles  will  slide  over  each  other, 
the  severed  attachments  being  immediately  made  good 
by  regelation.     It  will  not  yield  uniformly,  but  along 


CLOUDS  AND  RIVERS,  ICE  AND  GLACIERS.  191 

special  planes.  It  will  also  liquefy,  not  uniformly,  but 
along  special  surfaces.  Both  the  sliding  and  the  lique- 
faction will  take  place  principally  at  right  angles  to  the 
pressure,  and  glacier  lamination  is  the  result. 

490.  As  long  as  it  is  sound  the  laminated  glacier  ice 
resists  cleavage.     Regelation,  as  I  have  said,  makes  the 
severed  attachments  good.    But  when  such  ice  is  exposed 
to  the  weather  the  structure  is  revealed,  and  the  ice 
can  then  be  cloven  into  tablets  a  square  foot,  or  even  a 
square  yard  in  area. 

§  67.  Conclusion. 

491.  Here,   my  friend,  our  labours    close.     It   has 
been  a  true  pleasure  to  me  to  have  you  at  my  side  so 
long.    In  the  sweat  of  our  brows  we  have  often  reached 
the  heights  where  our  work  lay,  but  you  have  been 
steadfast  and  industrious  throughout,  using  in  all  pos- 
sible cases  your  own  muscles  instead  of  relying  upon 
mine.     Here  and  there  I  have  stretched  an  arm  and 
helped  you  to  a  ledge,  but  the  work  of  climbing  has 
been  almost  exclusively  your  own.     It  is  thus  that  I 
should  like  to  teach  you  all  things ;  showing  you  the 
way  to  profitable  exertion,  but  leaving  the  exertion  to 
you — more  anxious  to  bring  out  your  manliness  in  the 
presence  of  difficulty  than  to  make  your  way  smooth  by 
toning  difficulties  down." 

492.  Steadfast,  prudent,  without  terror,  though  not 


102  THE  FORMS   OF  WATER  IN  CLOUDS,  ETC. 

at  all  times  without  awe,  I  have  found  you  on  rock  and 
ice,  and  you  have  shown  the  still  rarer  quality  of 
steadfastness  in  intellectual  effort.  As  here  set  forth, 
our  task  seems  plain  enough,  but  you  and  I  know  how 
often  we  have  had  to  wrangle  resolutely  with  the  facts 
to  bring  out  their  meaning.  The  work,  however,  is  now 
done,  and  you  are  master  of  a  fragment  of  that  sure 
and  certain  knowledge  which  is  founded  on  the  faithful 
study  of  nature.  Is  it  not  worth  the  price  paid  for 
it  ?  Or  rather,  was  not  the  paying  of  the  price — the 
healthful,  if  sometimes  hard,  exercise  of  mind  and 
body,  upon  alp  and  glacier — a  portion  of  our  delight  ? 

493.  Here  then  we  part.  And  should  we  not  meet 
again,  the  memory  of  these  days  will  still  unite  us. 
Give  me  your  hand.  Good  bye. 


THE    WORKS    OF 

Prof;  JOHN  TYNDALL,  LLD.,  P.R.S. 


-   I. 
HEAT   AS   A   MODE   OF   MOTION. 

One  vol.,  I2mo.     Cloth,  $2.00. 

"  My  aim  has  been  to  rise  to  the  level  of  these  questions  from  a  basis  so  elementary  that 
a  person  possessing  any  imaginative  faculty  and  power  of  concentration  might  accom- 
pany me."— From  AUTHOR'S  PREFACE. 

II. 

ON   SOUND. 

A  Course  of  Eight  Lectures  delivered  at  the  Royal  Institution  of  Great 
Britain.     One  vol.     With  Illustrations.     I2mo.     Cloth^  $2.00. 
"  In  the  following  pages  I  have  tried  to  render  the  science  of  Acoustics  interesting  to 
all  intelligent  persons,  including  those  who  do  not  possess  any  special  scientific  culture." — 
From  AUTHOR'S  PREFACE. 

III. 

FRAGMENTS  OF  SCIENCE    FOR    UNSCIENTIFIC 
PEOPLE. 

A  Series  of  Detached  Essays,  Lectures,  and  Reviews.     One  vol.,  I2mo. 
Cloth,  $2.00. 

"  My  motive  in  writing  these  papers  was  a  desire  to  extend  sympathy  for  science  be- 
yond the  limits  of  the  scientific  public.  .  .  .  From  America  the  impulse  came  which  in- 
duced me  to  gather  these  '  Fragments,'  and  to  my  friends  in  the  United  States  I  dedicate 
them." — From  AUTHOR'S  PREFACE. 

IV. 

LIGHT   AND   ELECTRICITY. 

Notes  of  Two  Courses  of  Lectures  before  the  Royal  Institution  of  Great 
Britain.     One  vol.,  I2mo.     Cloth,  $1.25. 

"  In  thus  clearly  and  sharply  stating  the  fundamental  principles  of  Electrical  and  Op- 
tical Science,  Prof.  Tyndall  has  earned  the  cordial  thanks  of  all  interested  in  education."— 
From  AMERICAN  EDITOR'S  PREFACE. 

D.  APPLETON  &  CO.,  Publishers, 

549  &  551   Broadway,  N.  Y. 


THE    WORKS    OF 


Prof,  JOHN  TYNDALL,  LLD.,  F.R.S, 


v. 
HOURS  OF   EXERCISE    IN   THE   ALPS. 

One  vol.,  I2mo.     With  Illustrations.     Cloth,  $2.00. 

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those  who  find  exhilaration  in  descriptions  associated  with  mountain-life." — From  AUTHOR'S 
PREFACE. 

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One  vol.,  I2mo.     Cloth,  $1.00. 

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Faraday  as  a  scientific  investigator  and  discoverer I  have 

returned  from  my  task  with  such  results  as  I  could  gather,  and  also  with  the  wish  that 
these  results  were  more  worthy  than  they  are  of  the  greatness  of  my  theme." — The 
Author. 

VII. 

FORMS  OF  WATER,  IN   CLOUDS,   RAIN,   RIVERS,   ICE, 
AND   GLACIERS. 

This  is  the  first  volume  of  the  International  Scientific  Series,  and  is  a  valu- 
able and  interesting  work.     One  vol.,  I2mo.     Cloth,  $1.50. 

VIII. 

CONTRIBUTIONS  TO   MOLECULAR    PHYSICS   IN   THE 
DOMAIN   OF   RADIANT   HEAT. 

A  Series  of  Memoirs  published  in  the  "  Philosophical  Transactions  "  and 
"  Philosophical  Magazine."     With  Additions. 

D,  APPLETON  &  CO,,  Publishers, 

849  &  551  Broadway,  N.  Y. 


THE  INTERNATIONAL 
SCIENTIFIC    SERIES. 


D.  APPLETON  &  Co.  have  the  pleasure  of  announ- 
cing that  they  have  made  arrangements  to  issue  a  com- 
prehensive series  of  books,  under  the  above  title,  from 
eminent  men  of  different  countries.  Although  not  spe- 
cially designed  for  the  instruction  of  beginners,  these 
works  will  be  adapted  to  the  non-scientific  public,  and 
will  be,  as  far  as  possible,  explanatory  in  character  and 
free  from  technicalities.  The  character  and  scope  of  the 
works  will  be  best  illustrated  by  a  reference  to  the  names 
and  subjects  in  the  following  list : 

Professor  JOHN  TYNDALL,  LL.D,,  F.R.S. 

THE  FORMS   OF  WATER   IN   RAINS  AND   RIVERS,  ICE 
AND  GLACIERS. 

WALTER  BAGEHOT. 

PHYSICS  AND  POLITICS. 

Dr.  EDWARD  SlfflTH,  F.R.S. 

FOOD  AND  DIETS. 

Professor  T.  H.  HUXLEY,  LL.D.,  F.R.S. 

BODILY  MOTION  AND  CONSCIOUSNESS. 

Dr.  W.  B.  CARPENTER,  LL.D.,  F.R.S. 

THE  PRINCIPLES  OF  MENTAL  PHYSIOLOGY. 

Sir  JOHN  LTTBBOCK,  Bart.,  F.R.S. 

THE  ANTIQUITY  OF  MAN. 
i 


International  Scientific  Series. 


Professor  RUDOLPH  VIRCHOW  (of  the  University  of  Berlin). 
MORBID  PHYSIOLOGICAL  ACTION. 

Professor  ALEXANDER  BAIN,  LL.D. 

RELATIONS  OF  MIND  AND  BODY. 

Professor  BALFOUR  STEWART,  LL.D.,  F.R.S. 

THE  CONSERVATION  OF  ENERGY. 

Dr.  H.  CHARLTON  BASTIAN,  M.D.,  F.R.S, 

THE  BRAIN  AS  AN  ORGAN  OF  MIND. 

HERBERT  SPENCER,  Esq. 

THE  STUDY  OF  SOCIOLOGY. 

Professor  WILLIAM  ODLING,  F.R.S, 

THE  NEW  CHEMISTRY. 

Professor  W.  THISELTON  DYER,  B.A.,  B.Sc. 

FORM  AND  HABIT  IN  FLOWERING  PLANTS. 

Professor  W.  KINGDON  CLIFFORD,  M.A. 

THE     FIRST    PRINCIPLES    OF    THE    EXACT    SCIENCES 
EXPLAINED  TO  THE  NON-MATHEMATICAL. 

Mr.  J.  N.  LOCKYER,  F.R.S. 

SPECTRUM  ANALYSIS. 

W.  LATTDER  LINDSAY,  M.D.,  F.R.S.E. 

MIND  IN  THE  LOWER  ANIMALS. 

Dr.  J.  B.  PETTIGREW,  M.D.,  F.R.S. 

WALKING,  SWIMMING,  AND  FLYING. 

Professor  A.  C.  RAMSAY,  LL.D.,  F.R.S. 

EARTH  SCULPTURE  :  Hills,  Valleys,  Mountains,  Plains,  Rivers, 
Lakes ;  how  they  were  Produced,  and  how  they  have  been  Destroyed. 

Dr.  HENRY  MATJDSLEY. 

RESPONSIBILITY  IN  DISEASE. 

Professor  MICHAEL  FOSTER,  M.D. 

PROTOPLASM  AND  THE  CELL-THEORY. 


International  Scientific  Series. 


Rev.  M.  J.  BERKELY,  M.A.,  F.L.S. 

FUNGI:  their  Nature,  Influences,  and  Uses. 
Professor  CLAUDE  BERNARD  (of  the  College  of  France). 

PHYSICAL  AND  METAPHYSICAL  PHENOMENA  OF  LIFE. 

Professor  A.  QUETELET  (of  tlie  Brussels  Academy  of  Sciences). 
SOCIAL  PHYSICS. 

Professor  H.  SAINTE-CLAIRE  DEVILLE. 

AN  INTRODUCTION  TO  GENERAL  CHEMISTRY. 

Professor  WURTZ. 

ATOMS  AND  THE  ATOMIC  THEORY. 

Professor  D.  QUATREFAGES, 

THE  NEGRO  RACES. 

Professor  LACAZE-DTJTHIERS. 

ZOOLOGY  SINCE  CUVIER. 

Professor  BERTHELOT. 

CHEMICAL  SYNTHESIS. 
Professor  JAMES  D.  DANA,  M.A.,  LL.D. 

ON  CEPHALIZATION  ;  or,  Head  Domination  in  its  Relation  to 
Structure,  Grade,  and  Development. 

Professor  S.  W.  JOHNSON,  M.A. 

ON  THE  NUTRITION  OF  PLANTS. 

Professor  AUSTIN  FLINT,  Jr.,  M.D. 

THE  NERVOUS   SYSTEM   AND   ITS   RELATION  TO  THE 
BODILY  FUNCTIONS. 

Professor  W.  D.  WHITNEY. 

MODERN  LINGUISTIC  SCIENCE. 

Other  eminent  authors,  as  WALLACE,  HELMHOLTZ,  PARKS,  MILNE- 
EDWARDS,  ROSENTHAL,  and  H^ECKEL,  have  given  strong  encouragement 
that  they  will  also  take  part  in  the  enterprise. 

D.  APPLETON  &  CO.,  Publishers, 

549  and  551  Broadway,  N.  Y. 
3 


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4-X 


